Airbag Deployment Techniques

ABSTRACT

Airbag deployment system for a vehicle having a passenger compartment includes airbags arranged to substantially fill the passenger compartment upon deployment, an inflator system for inflating the airbags and a crash sensor system coupled to the inflator system for directing the inflator system to inflate the airbag. Multiple housings may be arranged around the passenger compartment, each including at least one airbag. Some of the airbags may be interconnected to provide a primary airbag and at least one secondary airbag extending from the primary airbag. The inflator system may be an aspirated inflator system. The crash sensor system may be an anticipatory sensor system. The airbags may be film airbags. One-way valves may be arranged between adjacent airbags.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/418,517 filed May 4, 2006 which is a divisional of U.S. patentapplication Ser. No. 11/131,623 filed May 18, 2005 which is:

1) a continuation-in-part (CIP) of U.S. patent application Ser. No.10/817,379 filed Apr. 2, 2004; and

2) a CIP of U.S. patent application Ser. No. 10/974,919 filed Oct. 27,2004, now U.S. Pat. No. 7,040,653.

This application is related to, on the grounds that it includes commonsubject as, U.S. patent application Ser. No. 10/413,318 filed Apr. 14,2003, U.S. patent application Ser. No. 09/888,575 filed Jun. 25, 2001,now U.S. Pat. No. 6,715,790, U.S. patent application Ser. No.09/535,198, filed Mar. 27, 2000, now U.S. Pat. No. 6,250,668, U.S.patent application Ser. No. 09/071,801, filed May 4, 1998, now U.S. Pat.No. 6,149,194, U.S. patent application Ser. No. 08/795,418, filed Feb.4, 1997, now U.S. Pat. No. 5,863,068, U.S. patent application Ser. No.08/626,493, filed Apr. 2, 1996, now U.S. Pat. No. 5,746,446, U.S. patentapplication Ser. No. 08/571,247, filed Dec. 12, 1995, now U.S. Pat. No.5,772,238, U.S. patent application Ser. No. 08/539,676, filed Oct. 5,1995, now U.S. Pat. No. 5,653,464, and U.S. patent application Ser. No.08/247,763, filed May 23, 1994 now U.S. Pat. No. 5,505,485.

All of the above applications and patents, and any applications,publications and patents mentioned below, are incorporated herein byreference in their entirety and made a part hereof.

FIELD OF THE INVENTION

The present invention relates to airbag deployment techniques.

The present invention also relates to airbags made from plastic filmsuch as a side curtain airbag arranged to deploy along the side of avehicle to protect occupants during a crash involving the vehicle,including a rollover. The side curtain airbag may even wrap around afront-seated occupant, i.e., have a frontal portion designed to deploybetween a front-seated occupant and the dashboard. Also there may be aplurality plastic film airbags that deploy in the event of a vehiclecrash. In some cases, such plastic film airbags may deploy to fillsubstantially all of the front passenger compartment of an automotive ortruck vehicle.

BACKGROUND OF THE INVENTION

The invention relates to several different areas and a discussion ofsome particular areas of interest follows. All mentioned patents,published patent applications and literature are incorporated byreference herein.

1. Airbags

1.1 Plastic Film Airbags

At the time of earlier related applications, plastic films had notpreviously been used to make airbags with the exception of perforatedfilms as disclosed in U.S. Pat. No. 4,963,412 to Kokeguchi, which isdiscussed below.

U.S. Pat. No. 3,451,693 (Carey) describes the presence of a variableexhaust orifice in an airbag which maintains constant pressure in theairbag as the occupant is thrown into the airbag but does not discloseplastic film, merely plastic. The distinguishable properties of film arenumerically described in the instant specification and basically arethinner and less weight. The material of Carey is not plastic film whichis capable of arresting the propagation of a tear. In fact, it isunclear in Carey as to whether the orifice can be varied in arepeatable/reusable manner and no mention is made as to whether thestretching of the orifice area is permanent or temporary.

U.S. Pat. No. 5,811,506 (Slagel) describes a thermoplastic, elastomericpolyurethane for use in making vehicular airbags. The polyurethane isextrudable so that airbags of various shapes and sizes can be formedtherefrom.

U.S. Pat. No. 6,627,275 (Chen) describes the use of crystal gels toachieve tear resistance for airbags. This is a particular example of theteachings herein for the use of the thermoplastic elastomers to achievetear resistance through the use of a particular subclass of suchpolymers. No mention is made, however, to laminate these materials witha film with a higher elastic modulus as is taught herein. Althoughinteresting materials, they may not be practical for airbags due totheir high cost. In particular, the crystal gel described in Chen ispart of a class of thermoplastic elastomer (TPE) and in particular ofpolyester elastomers such as HYTREL™ which are discussed elsewhereherein and in the parent applications listed above. It is important tonote that the particular formulations listed in Chen are probably poorchoices for the blunting film portion of a laminated film used to makefilm airbags. This is due to their very high elasticity of 10⁴ to 10⁶dynes per cm² (see Chen at col. 21, line 4). This corresponds to theliquid crystal polymers which have an elastic modulus of above 10¹⁰dynes per cm². Thus, they will provide little resistance to thepropagation of a tear in the higher modulus component of the laminatedfilm and would be poor as the blunting layer.

It is important to note that liquid crystal polymers of a different sortthan disclosed in Chen having quite the opposite properties would beideal candidates for the high modulus component of a laminated film dueto their inelastic nature, that is their high modulus of elasticity.Although these materials are considerably more expensive than NYLON®,for example, they are about twice as strong and therefore only half asmuch would be required. This would render the inner layer, for example,of a lamination with perhaps urethane as the outer layers, half thethickness and thus one eighth of the bending stiffness of NYLON®. Thus,the laminated airbag made in this manner would be considerably easier tofold and when folded, it would occupy substantially less space.

Another advantage of the more rigid liquid crystal polymers is that theycan be laminated to polyurethane or other blunting materials without theneed for an adhesive. This results in a significant cost saving for thelaminated film and thus partially offsets the higher cost of thematerial compared with NYLON®, for example. Naturally, they can also belaminated to a more elastic liquid crystal polymer.

Note also that the “soft, safe, hugging, enveloping inflatable restraintcushions” described in Chen are not applicable in the form disclosedbecause, if used in a thin film version, it would blow up like a balloonpermitting the occupant to easily displace the gas and penetrate farinto the airbag. If used in a thick film version so that it does notstretch, then the advantages of the material are lost and the airbagwould be similar in weight to a fabric airbag. However, if it islaminated to a more rigid material or a net as disclosed herein and inthe previous patents of the current assignee, then again many of theadvantages of the material are lost since the main material providingthe strength to the airbag is the more rigid film or net layer.Nevertheless, providing there is not too much of a cost penalty the“elastic-crystalline gels” described in Chen might be advantageouslyused in the inventions described herein for some applications. Someother patents assigned to the same assignee as Chen that may be relevantto inventions herein are: U.S. Pat. No. 6,552,109, U.S. Pat. No.6,420,475, U.S. Pat. No. 6,333,374, U.S. Pat. No. 6,324,703, U.S. Pat.No. 6,148,830, U.S. Pat. No. 6,117,176, U.S. Pat. No. 6,050,871, U.S.Pat. No. 5,962,572, U.S. Pat. No. 5,884,639, U.S. Pat. No. 5,868,597,U.S. Pat. No. 5,760,117, U.S. Pat. No. 5,655,947, U.S. Pat. No.5,633,286, U.S. Pat. No. 5,508,334, U.S. Pat. No. 5,336,708, U.S. Pat.No. 5,334,646, U.S. Pat. No. 5,324,222, U.S. Pat. No. 5,262,468 and U.S.Pat. No. 4,369,284.

Although airbags are now installed in all new vehicles and each year anincreasing number of airbags are making their way into new vehicledesigns, they are still basically the same design as originally inventedabout 40 years ago. Generally, each driver and passenger side airbag isa single chamber or at most two chambers, they are made from fabric thathas sufficient mass as to cause injury to an occupant that is in thedeployment path and they are positioned so that a forward-facingoccupant will be protected in a substantially frontal impact. Incontrast, many occupants are out-of-position and many real world crashesinvolved highly angular impacts, spinouts, rollovers etc. where theoccupant is frequently injured by the deploying airbag and impacts otherobjects in the vehicle compartment in addition to the airbag.

In the out-of-position case, occupant sensors are now being consideredto prevent or control the deployment of the airbag to minimizedeployment induced injuries. These occupant sensors will significantlyreduce the number of deaths caused by airbags but in doing so, they candeprive the occupant of the protection afforded by a softer airbag ifthe deployment is suppressed. Side and side curtain airbags are beinginstalled to give additional protection to occupants in side impacts androllovers. However, there still will be many situations where occupantswill continue to be injured in crashes where airbags could have been asignificant aid. What is needed is an airbag system that totallysurrounds the occupant and holds him or her in the position that he orshe is prior to the crash. The airbag system needs to deploy veryrapidly, contact the occupant without causing injury and prevent his orher motion until the crash is over. This is a system that fills up thepassenger compartment in substantially the same way that packagingmaterial is used to prevent breakage of a crystal glass during shipment.

To accomplish this self-adjusting airbag system, the airbags must bemade of very light material so that when they impact the occupant, theydo not cause injury. They also must be inflated largely with the gasthat is in the passenger compartment or else serious ear injuries mayresult and the doors and windows may be blown out. Thus, an airbagsystem comprised of many mini-airbags all connected together andinflated with one or more aspirated inflators that limit the pressurewithin each mini-airbag is needed. This is one focus of this invention.As it is accomplished, the inflators will get smaller and simpler sincethere will be no need for dual stage inflators. Since out-of-positionoccupants will not be injured by the deploying airbags, there will be noneed for occupant sensors and children can safely ride in the front seatof a vehicle. The entire system will deploy regardless of the directionof the impact and the occupants will be frozen in their pre-crashpositions until the crash is over.

Anticipatory crash sensors based on pattern recognition technology aredisclosed in several of current assignee's patents and pending patentapplications (see, e.g., U.S. Pat. No. 6,343,810, U.S. Pat. No.6,209,909, U.S. Pat. No. 6,623,033, U.S. Pat. No. 6,746,078 andUS20020166710). The technology now exists to allow the identificationand relative velocity determination to be made for any airbag-requiredaccident prior to the accident occurring (anticipatory sensing). Thisachievement now allows airbags to be reliably deployed prior to theaccident. The implications of this are significant. Prior to thisachievement, the airbag system had to wait until an accident startedbefore a determination could be made whether to deploy the airbags. Theresult is that the occupants, especially if unbelted, would frequentlyachieve a significant velocity relative to the vehicle passengercompartment before the airbags began to interact with the occupant andreduce his or her relative velocity. This would frequently subject theoccupant to high accelerations, in some cases in excess of 40 Gs, and inmany cases result in serious injury or death to the occupant. On theother hand, a vehicle typically undergoes less than a maximum of 20 Gsduring even the most severe crashes. Most occupants can withstand 20 Gswith little or no injury. Thus, as taught herein, if the accidentseverity could be forecast prior to impact and the vehicle filled withplastic film airbags that freeze the occupants in their pre-crashpositions, many lives could be saved and many injuries avoided.

A main argument against anticipatory sensors is that the mass of theimpacting object remains unknown until the accident commences. However,through using a camera, or other imaging technology based on, e.g.,infrared, radar or terahertz generators and receivers, to monitorpotentially impacting objects and pattern recognition technologies suchas neural networks, the object can be identified and in the case ofanother vehicle, the mass of the vehicle when it is in the unloadedcondition can be found from a stored table in the vehicle system. If thevehicle is a commercial truck, then whether it is loaded or not willhave little effect on the severity of an accident. Also if the relativevelocity of the impacting vehicles is above some threshold, then againthe mass of the impacting vehicle is not important to the deploymentdecision. Pickup trucks and vans are thus the main concern because asloaded, they can perhaps weigh 50 percent more than when unloaded.However, such vehicles are usually within 10% of theirunloaded-plus-one-passenger weight almost all of the time. Since thedecision to be made is whether or not to deploy the airbag, in allsevere cases and most marginal cases, the correct decision will be madeto deploy the airbag regardless if there is additional weight in thevehicle. If the assumption is made that such vehicles are loaded with nomore than 10% additional weight, then only in a few marginal crashes, ano-deployment decision will be made when a deployment decision iscorrect. However, as soon as the accident commences, the traditionalcrash sensors will detect the accident and deploy the airbags, but forthose marginal cases the occupants will have obtained little relativeforward velocity anyway and probably not be hurt and certainly notkilled by the deploying plastic film airbags which stop deploying assoon as the occupant is contacted. Thus, the combination of anticipatorysensor technology and plastic film airbags as disclosed herein resultsin the next generation self adapting safety system that maximizesoccupant protection. Both technologies preferably can be used together.

Another feature of plastic film airbags discussed below is the abilityof film to be easily joined together to form structures that would bedifficult or impossible to achieve with fabric such as the addition of asheet of film to span the chambers of a side curtain airbag. It is wellknown that side curtain airbags are formed with chambers in order tolimit the thickness of the curtain. This results in a curtain withreduced stiffness to resist the impact of the head of an occupant, forexample, and to also form areas where the protection is less than otherareas due to the presence of seams. Using film, these seam sections canbe easily spanned without running the risk of introducing additionalleakage paths in the airbag. This spanning of the chambers can produceadditional chambers that can also be pressurized or the additionalchambers can be left open to the atmosphere.

An analysis of a driver airbag made from two flat sheets of inelasticfilm shows that maximum stresses occur in the center of the airbag wherethe curvature is at a minimum. Thus, the material strength and not theseal or seam strength limits the pressure that causes the airbag tofail. On the other hand, analysis of some conventional side curtainairbags has shown that maximum stress can occur in the seams and thusthe maximum pressure that the airbag can hold without bursting islimited by the material strength in the seams. This fact is at leastpartially the cause of excessive gas leakage at the seams of some fabricairbags necessitating the lamination of a polymer film onto the outsideof the airbag. This problem is even more evident when the bag is made bycontinuous weaving where the chambers are formed by weaving two sheetsof material together. A solution to this problem as discussed below isto first optimize the design of the seam area to reduce stresses andthen to form the airbag by joining the sheets of material by heatsealing, for example, where an elastic material forms the seam thatjoins the sheets together. Such a joint permits the material to stretchand smooth the stresses, eliminating the stress concentrations and againplacing the maximum stresses in the material at locations away from theseam. This has the overall effect of permitting the airbag to beconstructed from thinner material permitting a more rapid deployment andcausing less injury to an out-of-position occupant. This technique alsofacilitates the use of plastic film as an airbag material. Such a filmcan comprise a relatively inelastic, biaxially oriented layer formaximum tensile strength and a relatively elastic, polyurethane film, orequivalent, where the polyurethane film is substantially thicker thanthe NYLON®. This combination not only improves the blunting propertydiscussed above but also substantially reduces the stresses in the seams(see Appendix 3 of U.S. patent application Ser. No. 10/817,379).

U.S. Pat. No. 6,355,123 to Baker et al. uses reinforcement material tomake the seams stronger so as to compensate for the increased stressesdiscussed above rather than using elastic material to smooth out thestresses as disclosed herein. Similarly, in U.S. Pat. No. 6,712,920,Masuda et al. add reinforcing strips to the inside of a seam which areattached by adhesive to the airbag beyond the sewn seam.

1.2 Driver Side Airbag

A conventional driver side airbag (also referred to herein as a driverairbag) is made from pieces of either NYLON® or polyester fabric thatare joined together, e.g., by sewing. The airbag is usually coated onthe inside with neoprene or silicone for the purposes of (i) capturinghot particles emitted by the inflator in order to prevent holes frombeing burned in the fabric, and (ii) sealing the airbag to minimize theleakage of an inflating gas through the fabric. Although such coatingsare films, they differ significantly from the films disclosed herein inthat they do not significantly modify the properties of the fabricairbags to which they are applied since they are thin and substantiallymore elastic than fabric. These airbags are conventionally made by firstcutting two approximately circular sections of a material having acoating on only one side and which will form a front panel and a backpanel, and sewing them together with the coated side facing out. Theback panel is provided with a hole for attachment to an inflator. Fabricstraps, called tethers, are then sewn to the front panel. Afterwards,the airbag is turned inside out by pulling the fabric assembly throughthe inflator attachment hole placing the coated side on the inside.Assembly is completed by sewing the tethers to the back panel adjacentthe inflator attachment hole.

If a conventional driver airbag is inflated without the use of tethers,the airbag will usually take an approximately spherical shape. Such aninflated airbag would protrude significantly into the passengercompartment from the steering wheel and, in most cases, impact andinjure the driver. To prevent this possible injury, the tethers areattached to the front and rear panels of the airbag to restrict thedisplacement of the front panel relative to the back panel. The resultof the addition of such tethers is an airbag that has the shape of aflat ellipsoid with a ratio of the thickness of the airbag to itsdiameter of approximately 0.6. In the conventional airbag, the tethersare needed since the threads that make up the airbag fabric are capableof moving slightly relative to each other. The airbag is elastic forstresses that are not aligned with the warp or woof of the fabric. As aresult, the fabric would distort to form an approximate sphere in theabsence of such tethers.

Moreover, the above-mentioned method of manufacturing an airbag involvesa great deal of sewing and thus is highly labor intensive and, as aresult, a large percentage of all driver airbags are presentlymanufactured in low labor cost countries such as Mexico.

Many people are injured and some killed by interaction with thedeploying airbag (see, e.g., “Warning: Too Much Safety May BeHazardous”, New York Times, Sunday, Dec. 10, 1995, Section F, Page 8).One of the key advantages of the film airbag described herein and in thecurrent assignee's above-referenced patents and patent applications isthat, because of its much lower mass than conventional NYLON® orpolyester fabric airbags, the injury caused by interaction with thedeploying airbag is substantially reduced. In accordance with theteachings of those patents and patent applications mentioned above, thedriver airbag system can be designed to permit significant interactionwith the driver. In other words, the film airbag can be safely designedto intrude substantially further into the passenger compartment withoutfear of injuring the driver. Nevertheless, in some cases, as describedin U.S. Pat. No. 5,653,464, it may be desirable to combine theproperties of a film airbag, which automatically attains theconventional driver airbag shape, with a fabric airbag. In such cases,interaction with the driver needs to be minimized.

Airbag systems today are designed so that ideally the airbag is fullyinflated before the occupant moves into the space that is occupied bythe airbag. However, most occupants are not positioned at the ideallocation assumed by the airbag system designer, and also may not havethe dimensions, e.g., size and weight, in the range considered foroptimum airbag deployment by the airbag system designer. Many occupantssit very close to the airbags, or at least closer than expected by theairbag system designer, and as mentioned above, are injured by theairbag deployment. On the other hand, others sit far from the airbag, orat least farther away from the airbag than expected, and therefore musttravel some distance, achieving a significant relative velocity, beforereceiving the benefit of the airbag (see, e.g., “How People Sit in Cars:Implications For Driver and Passenger Safety in Frontal Collisions—TheCase for Smart Restraints.”, Cullen, E., et al 40^(th) AnnualProceedings, Association For the Advancement of Automotive Medicine, pp.77-91).

With conventionally mounted airbags such as those mounted in thesteering wheel or instrument panel, severe out-of-position occupantsituations, for example where the occupant is resting against the airbagwhen deployment begins, can be handled using an occupant positionsensor, such as disclosed in the current assignee's U.S. Pat. No.5,653,462 (corresponding to WO 94/22693) which prevents an airbag fromdeploying if an occupant is more likely to be seriously injured by theairbag deployment than from the accident itself. In many less severeaccidents, the occupant will still interact with the deploying airbagand sustain injuries ranging from the mild to the severe. In addition,as mentioned above, some occupants sit very far from the steering wheelor instrument panel and, with conventional airbags, a significantdistance remains between the occupant and the inflated airbag. Suchoccupants can attain a significant kinetic energy relative to the airbagbefore impacting it, which must be absorbed by the airbag. This effectserves to both increase the design strength requirements of the airbagand increase the injury induced in the occupant by the airbag. For thesereasons, it is desirable to have an airbag system that adjusts to thelocation of the occupant and which is designed so that the impact of theairbag causes little or no injury to the occupant.

Conventional airbags contain orifices or vent holes for exhausting orventing the gas generated by the inflator. Thus, typically for frontalimpact airbags within one second after the bag is inflated (and hasprovided its impact absorbing function), the gas has been completelyexhausted from the bag through the vent holes. This imposes severallimitations on the restraint system that encompasses the airbag system.Take for example the case where an occupant is wearing a seatbelt andhas a marginal accident, such as hitting and severing a small tree,which is sufficient to deploy the airbag, but where it is not reallyneeded since the driver is being restrained by his seatbelt. If thedriver has lost control of the car and is traveling at 30 MPH, forexample, and has a secondary impact one second or about 50 feet later,this time with a large tree, the airbag will have become deflated andthus is not available to protect the occupant in this secondary, lifethreatening impact.

In other situations, the occupant might be involved in an accident thatexceeds the design capability of the restraint system. These systems aretypically designed to protect an average-size male occupant in a 30-MPHbarrier impact. At higher velocities, the maximum chest decelerationexperienced by the occupant can exceed 60 G's and become lifethreatening. This is particularly a problem in smaller vehicles, whereairbag systems typically only marginally meet the 60-G maximumrequirement, or with larger or frailer occupants.

There are many cases, particularly in marginal crashes, where existingcrash sensors will cause the airbag to deploy late in the crash. Thiscan also result in an “out-of-position occupant” for deployment of theairbag that can cause injuries and possibly death to the occupant. Othercases of out-of-position occupants include standing children or theforward motion of occupants during panic braking prior to impactespecially when they are not wearing seatbelts. The deploying airbag inthese situations can cause injury or death to the out-of-positionoccupant. It is estimated that more than one hundred people have nowbeen killed and countless more seriously injured by the deployment ofthe airbag due to being out-of-position.

It is recognized in the art that the airbag must be available to protectan occupant for at least the first 100-200 milliseconds of the crash andlonger for rollover events. Since the airbag usually contains largevents, the inflator must continue to supply gas to the airbag to replacethe gas flowing out of these vents. As a result, inflators are usuallydesigned to produce about twice as much gas than is needed to fill theairbag for frontal impacts. This, of course, increases the cost of theairbag system as well as its size, weight, pressure in the passengercompartment and total amount of contaminants resulting from the gasesthat are exhausted into the automobile environment.

This problem is compounded when the airbag becomes larger, which is nowpossible using the film materials of this invention, so as to impactwith the occupant wherever he/she is sitting, without causingsignificant injury, as in a preferred implementation of this invention.This then requires an even larger inflator which, in many cases, cannotbe accommodated in conjunction with the steering wheel, if conventionalinflator technology, rather than an aspirated inflator, is utilized.

Furthermore, there is a great deal of concern today for the safety of achild in a rear facing child seat when it is used in the front passengerseat of a passenger airbag equipped vehicle. Current passenger sideairbags have sufficient force to cause significant injury to a childsitting in such a seat and parents are warned not to use child seats inthe front seat of a vehicle having a passenger side airbag.Additionally, several automobile companies are now experimenting withrear seat airbags in which case, the child seat problem would becompounded.

Airbags made of plastic film are described in the patents and patentapplications referenced above. Many films are quite inelastic undertypical stresses associated with an airbag deployment. If an airbag ismade from a pair of joined flat circular sections of such films andinflated, instead of forming a spherical shape, it automatically formsthe flat ellipsoidal shape required for driver airbags as described inU.S. Pat. No. 5,653,464. This unexpected result vastly simplifies themanufacturing process for driver airbags since tethers are not required,i.e., the film airbag is made from two pieces of film connected only attheir peripheral edges. Furthermore, since the airbag can be made byheat-sealing two flat circular sections together at their peripheraledges without the need for tethers, the entire airbag can be madewithout sewing, thereby reducing labor and production costs. In fact,the removal of the requirement for tethers permits the airbag to be madeby a blow molding or similar process which greatly reduces the cost ofmanufacturing driver airbags. Thus, the use of film for making an airbaghas many advantages that are not obvious.

Films having this inelastic quality, that is films with a high modulusof elasticity and low elongation at failure, tend to propagate tearseasily and thus when used alone are not suitable for airbags. Thisproblem can be solved through the addition of reinforcement inconjunction with the inelastic films such as a net material as describedin the above-referenced patents and patent applications. Other moreelastic films such as those made from the thermoplastic elastomers, onthe other hand, have a low modulus of elasticity and large elongation atfailure, sometimes 100%, 200% or even 400%, and naturally resist thepropagation of tears. Such films, on the other hand, do not form theflat ellipsoidal shape desired for steering wheel-mounted driver sideairbags. As discussed in greater detail below, the combination of thetwo types of film through attachment using lamination, successivecasting or coating, or through the use of adhesives, which can beapplied in a pattern, can produce a material having both theself-shaping and the resistance to tear propagation properties.

In addition to the above-referenced patents and patent applications,film material for use in making airbags is described in U.S. Pat. No.4,963,412 to Kokeguchi. The film airbag material described in Kokeguchiis considerably different in concept from that disclosed in the currentassignee's above-referenced patents and patent applications or theinstant invention. The prime feature of Kokeguchi is that the edge tearresistance, or notch tear resistance, of the airbag film material can beincreased through the use of holes in the plastic films, i.e., the filmis perforated. Adding holes, however, reduces the tensile strength ofthe material by a factor of two or more due to the stress concentrationeffects of the hole. It also reduces the amount of available material toresist the stress. As such, it is noteworthy that the Kokeguchi steeringwheel mounted airbag is only slightly thinner than the conventionaldriver side fabric airbag (320 micrometers (0.013 inches) vs. theconventional 400 micrometers) and is likely to be as heavy as or perhapsheavier than the conventional airbag. Also, Kokeguchi does not discloseany particular shapes of film airbags or even the airbag itself for thatmatter. Since his airbag has no significant weight advantage overconventional airbags, there is no teaching in Kokeguchi of perhaps themost important advantage of thin film airbags of the present invention,that is, in reducing injuries to occupants who interact with a deployingairbag.

In some implementations of the film airbag of the present invention, theconcept of “blunting” is used to achieve the property of arresting thepropagation of a tear (see, e.g., Weiss, Peter “Blunt Answer: Crackingthe puzzle of elastic solids' toughness”, Science News, Week of Apr. 26,2003, Vol. 163, No. 17).

As discussed in detail below, the airbags constructed in accordance withthe present teachings attain particular shapes based on the use of theinelastic properties of particular film materials and reduce tearpropagation through a variety of novel methods including the use ofelastic films and blunting that is achieved by combinations of filmswith different elastic moduli. It is also noteworthy that Kokeguchidescribes using vacuum methods to form the airbag into the desired shapeand thus fails to realize that the properties of inelastic film resultsin the airbag automatically forming the correct shape upon deployment.Also noteworthy is that Kokeguchi states that polymeric films do nothave sufficient edge tear resistance and thus fails to realize thatfilms can be so formulated to have this property, particularly thosemade incorporating elastomers. These limitations of Kokeguchi results ina very thick airbag that although comprised of film layers, no longerqualifies as a true film airbag as defined herein.

A “film airbag” for the purposes herein is one wherein the filmthickness is generally less than about 250 micrometers (0.01 inches),and preferably even below about 100 micrometers, for use as a driverprotection airbag. As the size of the airbag increases, the thicknessmust also increase in order to maintain an acceptable stress within thefilm. A film airbag so defined may also contain one or more sectionsthat are thicker than about 250 micrometers and which are used primarilyto reinforce the thinner film portion(s) of the airbag. A film airbag asdefined herein may also include a layer or layers of inelastic materialand a layer or layers of elastic material (for example thermoplasticelastomers).

The neoprene or silicone coating on conventional driver airbags, asmentioned above, serves to trap hot particles that are emitted from someinflators, such as a conventional sodium azide inflator. A film airbagmay be vulnerable to such particles, depending on its design, and as aresult, cleaner inflators that emit fewer particles are preferred overmost sodium azide inflators. It is noteworthy, however, that even if ahole is burned through the film by a hot particle, the use of anelastomer in the film material prevents this hole from propagating andcausing the airbag to fail, that is by blunting the crack or tearpropagation. Also, new inflators using pyrotechnic, hybrid, aspirated orstored gas technologies are now available which do not produce hotparticles and produce gases which are substantially cooler than gasesproduced by sodium azide inflators. Also, not all sodium azide inflatorsproduce significant quantities of hot particles.

One interesting point that also is not widely appreciated by thoseskilled in the art previously, is that the gas temperature from theinflator is only an issue in the choice of airbag materials during theinitial stages of the inflation. The total thermal energy of the gas inan airbag is, to a first order approximation, independent of the gastemperature which can be shown by application of the ideal gas laws.When the gas initially impinges on the airbag material during the earlystages of the inflation process, the temperature is important and, if itis high, care must be taken to protect the material from the gas. Also,the temperature of the gas in the airbag is important if the vent holesare located where the out-flowing gas can impinge on an occupant. Theaverage temperature of the airbag itself, however, will not be affectedsignificantly by the temperature of the gas in the airbag.

In certain conventional airbag deployments, the propellant which is usedto inflate the airbag also is used to force open a hole in the vehicletrim, called the deployment door, permitting the airbag to deploy. Sincethe mass of a film airbag is substantially less than the mass of aconventional fabric airbag, much less energy is required to deploy theairbag in time. However, substantial pressure is still required to openthe deployment door. Also, if the pressure now used to open thedeployment door is used with film airbags, the airbag velocity once thedoor has been opened may be substantially higher than conventionalairbags. This rapid deployment can put excessive stresses on the filmairbag and increases the chance that the occupant will be injuredthereby. For most implementations of the film airbag, an alternate lessenergetic method of opening the deployment door may be required.

One such system is described in Barnes et al. (U.S. Pat. No. 5,390,950)entitled “Method and arrangement for forming an airbag deploymentopening in an auto interior trim piece”. This patent describes a method“ . . . of forming an airbag deployment opening in an interior trimpiece having a vinyl skin overlying a rigid substrate so as to beinvisible prior to operation of the airbag system comprising an energygenerating linear cutting element arranged in a door pattern beneath theskin acting to degrade or cut the skin when activated.”

A goal of Barnes et al. is to create an invisible seam when thedeployment door is located in a visible interior trim panel. Thispermits greater freedom for the vehicle interior designer to create theparticular aesthetic effect that he or she desires. The invisible seamof Barnes et al. is thus created for aesthetic purposes with no thoughttoward any advantages it might have to reduce occupant injury oradvantages for use with a film airbag, or to reduce injuries at all forthat matter. One unexpected result of applying the teachings of thispatent is that the pressure required to open the deployment door,resulting from the force of the inflating airbag, is substantiallyreduced. When used in conjunction with a film airbag, this result isimportant since the inflator can be designed to provide only sufficientenergy to deploy and inflate the very light film airbag therebysignificantly reducing the size of the inflator. The additional energyrequired to open a conventional deployment door, above that required toopen a deployment door constructed in accordance with the teachings ofBarnes et al., is not required to be generated by the inflator.Furthermore, since a film airbag can be more vulnerable to being injuredby ragged edges on the deployment door than a conventional fabricairbag, the device of Barnes et al. can be used to pyrotechnically cutopen the deployment door permitting it to be easily displaced from thepath of the deploying airbag, minimizing the force of the airbag againstthe door and thus minimizing the risk of damage to the film airbag fromthe deployment door. Since Barnes et al. did not contemplate a filmairbag, advantages of its use with the pyrotechnically openingdeployment door could not have been foreseen. Although Barnes et al.describes one deployment door opening method which is suitable for usewith an airbag made from plastic film as disclosed herein, i.e., onewhich requires substantially less force or pressure to open thanconventional deployment doors, other methods can be used in accordancewith the invention without deviating from the scope and spirit thereof.

The discussion of the self-shaping airbag thus far has been limited tofilm airbags. An alternate approach is to make an airbag from acombination of fabric and film. The fabric provides the tear resistanceand conventional airbag appearance. The film forces the airbag toacquire the flat ellipsoidal shape desired for driver airbags withoutthe use of tethers and permits the airbag to be assembled without sewingusing heat and/or adhesive sealing techniques. Such a hybrid airbag ismade from fabric and film that have been laminated together prior to thecutting operation. A combination of a film and net, as described in theabove referenced patents and patent applications, is equally applicablefor airbags described here and both will be referred to herein as hybridairbags and belong to the class of composite airbags. Combinations of afilm and fabric in this invention differ from previous neoprene orsilicone coated fabric airbags in that in the prior art cases, thecoating does not materially effect either the elastic modulus,stiffness, strength or tear resistance of the airbag whereas ininventions disclosed herein, the film contributes significantly to oneor more of these properties.

A finite element analysis of conventional driver side airbags (made offabric) shows that the distribution of stresses is highly unequal.Substantial improvements in conventional airbag designs can be made byredesigning the fabric panels so that the stresses are more equalized(see, e.g., Appendix 1 of U.S. patent application Ser. No. 10/974,919which describe inventive designs of airbags with fabric panels andrelatively more equalized stresses and Appendices 1-6 of U.S. patentapplication Ser. No. 10/817,379 filed Apr. 2, 2004, both of which areincorporated by reference herein). Today, conventional airbags aredesigned based on the strength required to support the maximum stressregardless of where that stress occurs. The entire airbag must then bemade of the same thickness material as that selected to withstandmaximum stress condition. This is wasteful of material and attempts havebeen made to redesign the airbag to optimize its design in order to moreclosely equalize the stress distribution and permit a reduction infabric strength and thus thickness and weight. However, thisoptimization process when used with conventional fabric airbags can leadto more complicated assembly and sewing operations and more expensivewoven materials and thus higher overall manufacturing costs. An exampleof such an airbag is that marketed by Precision Fabrics of Greensboro,N.C. Thus, there is a tradeoff between manufacturing cost and airbagoptimization.

As discussed in the above-referenced patents and patent applications aswell as below and in Appendix 1 of the '919 application and Appendices1-6 of the '379 application, with a film airbag manufactured using blowmolding or casting techniques, for example, greater freedom is permittedto optimize the airbag vis-à-vis equalization of the stress. First,other than tooling cost, the manufacturing cost of an optimized airbagis no greater than for a non-optimized airbag and in fact frequentlyless since less material is required. Furthermore, the thickness of thefilm can be varied from one part of the airbag to another to permit theairbag to be thicker where the stresses are greater and thinner wherethe stresses are less. A further advantage of blow molding or casting isthat the film can be made of a single constituent material. When theairbag is fabricated from sheet material, the outside layer of thematerial needs to be heat sealable, such as is the case withpolyurethane, polyethylene or other polyolefin, or else a specialadhesive layer is required where the sealing occurs.

As discussed in greater detail below in connection with the descriptionof the invention, when the film for the airbag is manufactured bycasting or coating methods, techniques familiar to those skilled in theart of plastics manufacturing are also available to produce a film wherethe thickness varies from one part to another in a predeterminedpattern. This permits a film to be made that incorporates thickersections in the form of a lattice, for example, which are joinedtogether with thin film. Thus, the film can be designed so thatreinforcing ribs, for example, are placed at the optimum locationsdetermined by mathematical stress analysis.

One example of an inflatable film product which partially illustratesthe self-shaping technology of this invention is the common balloon madefrom metallized MYLAR® plastic film found in many stores. Frequentlythese balloons are filled with helium. They are made by heat-sealing twoflat pieces of film together as described in U.S. Pat. No. 5,188,558(Barton), U.S. Pat. No. 5,248,275 (McGrath), U.S. Pat. No. 5,279,873(Oike) and U.S. Pat. No. 5,295,892 (Felton). Surprisingly, the shape ofthese balloons, which is circular in one plane and elliptical in theother two planes, is very nearly the shape that is desired for a driverside airbag. This shape is created when the pressure within the balloonis sufficiently low such that the stresses induced into the film aremuch smaller than the stresses needed to significantly stretch the film.The film used is relatively rigid and has difficulty adjusting to form aspherical shape. In contrast, the same airbag made from woven materialmore easily assumes an approximate spherical shape requiring the use oftethers to create the shape which comes naturally with the MYLAR®balloons.

One problem with film balloons is that when a hole is formed in theballoon, it fails catastrophically. One solution to this problem is touse a combination of a film and net as described in the currentassignee's above-referenced patents and patent applications. Suchmaterials have been perfected for use as sail material for lightweighthigh performance sails for sailboats. One example is marketed under thetrade name Bainbridge Sailcloth SL Series™, and in particular SL 500-P™,0.0015 inches. This material is a laminate of a film and a net. Suchmaterials are frequently designed to permit heat-sealing therebyeliminating threads and the stress concentrations associated therewith.Heat-sealing also simplifies the manufacturing process for making sails.Another preferred solution is to make the airbags from a film materialwhich naturally resists tears, that is, one which is chemicallyformulated to arrest a tear which begins from a hole, for example.Examples of films which exhibit this property are those from thethermoplastic elastomer (TPE) families such as polyurethane, Ecdelelastomer from Eastmen, polyester elastomers such as HYTREL™ and somemetallocene-catalyzed polyolefins. For the purposes herein, athermoplastic elastomer will include all plastic films which have arelatively low modulus of elasticity and high elongation at failure,including but not limited to those listed above. As discussed below, inmany implementations, the elastomers can be laminated with NYLON® (NYLON6,6 for example) or other more rigid film to form a composite filmhaving the blunting property.

Applications for the self-shaping airbag described herein include allairbags within the vehicle which would otherwise require tethers orcomplicated manufacturing from several separate panels. Most of theseapplications are more difficult to solve or unsolvable usingconventional sewing technology. The invention described herein solvessome of the above problems by using the inelastic properties of film,and others by using the elastic properties of thermoplastic elastomersplus innovative designs based on analysis including mathematicalmodeling plus experimentation (see Appendix 1 of the '919 applicationand Appendices 1-6 of the '379 application). In this manner, theproblems discussed above, as well as many others, are alleviated orsolved by the airbags described below. Films for airbags which exhibitboth the self-shaping property and also formulated to resist thepropagation of a tear are made by combining a layer of high modulusmaterial with a layer of a thermoplastic elastomer. Then, if a tearbegins in the combined film, it will be prevented from propagating bythe elastomer, yet the airbag will take the proper shape due to theself-shaping effect of the high modulus film. Such materials frequentlyexhibit blunting.

Japanese Patent No. 89-090412/12 describes fabricated cloths that arelaminated in layers at different angles to each other's warp axis to beintegrated with each other. Strength and isotropy are improved. Thecloth is stated as being useful for automotive airbags for protectingthe passenger's body. It is possible that such an airbag may have someof the self-shaping properties of a driver side film airbag disclosedherein but such is not disclosed in this patent.

U.S. Pat. No. 6,607,796 and U.S. Pat. No. 6,180,044 (Hirai) describe aplastic film driver side airbag referred to as a Resin airbag and amethod of making it. One layer of the film airbag is actually molded inplace resulting in a variation in material thickness at the seams. Thisvariation in thickness has also been disclosed in the current assignee'spatents as listed above. The resulting bag has a variation in the shapecaused by the variable width of the seam. In the current assignee'spatents, a similar effect is achieved by varying the geometry of theseam as illustrated herein in FIG. 5D.

Consider now a driver side airbag that does not rotate with the steeringwheel. Self-contained driver side airbag systems, such as U.S. Pat. No.4,167,276 to Bell and U.S. Pat. No. 4,580,810 to Thuen, are designed tomount on and rotate with the steering wheel of vehicles. Such designshave the advantage of being modular so that they can be installed onmany different vehicles with a modification of the steering wheel.However, because the airbag module rotates with the steering wheel, theshape of a driver side airbag must be axis-symmetrical with respect tothe axis of steering wheel, as is the case with conventional driverairbags. This configuration allows the airbag to deploy and provide auniform protection at any steering position. Usually a driver sideairbag is made of two circular pieces of coated NYLON® cloth sewntogether with tethers and becomes an approximation of an ellipsoid wheninflated.

An airbag absorbs the energy of an occupant when the occupant movesforward and impacts with the airbag and the airbag deforms to wraparound the occupant. The efficiency of an airbag cushion depends notonly on the stiffness and damping of the bag (which is a function of thepressure inside the bag and the exit orifices or exit valves), but alsoon the relative orientation and penetration of the occupant and the bag.If a large portion of the occupant torso is in contact with the bag inthe early stage of a crash, a considerable amount of occupant energy canbe dissipated. On the other hand, if only a small portion of the body,such as the head, is in contact with the bag, it can result insignificant penetration into the bag and delay the absorption of kineticenergy. Airbags of axis-symmetrical shapes may not be optimal foroccupant protection because the interaction between an airbag and anoccupant is a function of the distance and the relative angle betweenthe steering wheel and the occupant's upper torso. Another concern isthat the steering wheel angle can change significantly from driver todriver

Another problem of an ellipsoidal driver side bag is the tendency of thedriver to slide off edges of the bag particularly in angle crashes. Thisis mainly due to the geometry of the bag and the fact that the centralportion of the bag is frequently stiffer than the periphery. A solutionis to have a larger airbag, like a passenger side airbag, to embrace thedriver as much as possible to prevent the tendency to slide off theairbag. Such improvements cannot be achieved by a driver side airbagfixed to the steering wheel because the space and the geometry are bothlimited.

Some vehicles, such as buses and trucks, have a very steep steeringcolumn angle. When an accident occurs and the driver moves forward, thelower part of the steering wheel close to the driver makes contact withthe driver first and a great deal of abdomen or chest penetrationoccurs. If a conventional airbag module attached to the steering wheelis deployed, the protection of driver is limited until the upper torsoof the driver bends fully forward and lands on the air cushion. Thisproblem could be solved by modifying the angle of the steering wheel orcolumn, but it requires a change of the structure of the steeringmechanism or the installation of an additional joint in the steeringcolumn.

Inside a self-contained airbag module, the sensor is arranged so thatits axis is aligned to the axis of the steering wheel. The axis of thesensor is defined as the sensitive axis of the accelerometer or sensingmass. However, a ball-in-tube sensor or an accelerometer-based satellitecrush zone mounted sensor used to detect frontal impacts has thesensitive axis parallel to the longitudinal axis of the vehicle. Withsuch an arrangement, the sensor is most sensitive in the desireddetecting direction. In the self-contained module mounted on thesteering wheel, on the other hand, the sensitivity of the sensor to thefrontal velocity change is reduced because the sensor is inclined at anangle from the crushing direction. Even though the calibration of asensor can be chosen selected to compensate the steering column angle,this makes the sensor more sensitive to vertical accelerations which maybe undesirable.

In many cases, the driver side airbag module located on the steeringwheel is large and frequently blocks the driver's view of the instrumentpanel behind the steering wheel. When this is the case, the addition ofan airbag system to a vehicle can require modification of the steeringcolumn or the instrument panel to compensate for this reducedvisibility.

The steering column of some vehicles may collapse or shift in ahigh-speed crash or under a tremendous crush of the front end of avehicle. If the driver side airbag is designed to operate under normalconditions, the unexpected movement of the steering column could changethe location of a deployed airbag and thus alter the relative positionsof the occupant and the airbag cushion. This can result in a partialloss of airbag protection for the driver.

US20040026909 to Rensingoff describes an auxiliary airbag coming fromthe dashboard to support the steering wheel and provide additionalprotection to the driver through this supplemental airbag. Such anairbag is not disclosed to aid in supporting a much lighter steeringwheel steering column as might be used in a drive-by-wire system.

1.3 Passenger Side Airbag

There is no known related art specifically covering passenger airbagsmade from plastic film.

1.4 Inflatable Knee Bolster

This aspect of the invention relates to a knee bolster safety apparatusfor protecting the legs and lower torso of the occupant of a motorvehicle to reduce the extent and severity of injuries sustained during acrash. This invention more specifically relates to using an inflatablebolster to restrain the occupant's legs and lower torso during asurvivable crash.

During a frontal impact, the occupant moves forward due to the inertiaand kinematics of the crash while the front components of the vehiclestructure (bumper, hood, engine cavity) begin to collapse. Knee and leginjuries can occur when the body of an occupant slides or submarinesforward and/or downward and the occupant's knees hit the instrumentpanel or structure beneath the panel. Further injuries can occur whenthe occupant's lower torso and legs move forward such that the knees aretrapped in or beneath the instrument panel just before the foot wellbegins to collapse. As the foot well collapses, it can push theoccupant's feet backward, causing the knees to elevate and becomefurther trapped. As the foot well continues to crush, the loads on thetrapped legs increase and can cause foot, ankle, and tibia injuries.These injuries are common even with fixed knee bolsters designed to meetpresent knee injury criteria requirements.

Abdominal and lower torso injuries can be inflicted by the lap and lowerpart of the torso belts as they ride upward on the soft tissue of theoccupant's torso when he or she slides forward and downward due to theforces of the frontal crash. Knee bolsters are designed to attempt toeliminate or minimize these injuries.

Airbag apparatus are generally designed under the assumption that theoccupant is riding in the vehicle in a forward-facing, seated positionwith both feet on the vehicle floor. When an occupant is not in thisposition, the occupant or occupant's body part is said to be“out-of-position”. As most occupants are sometimes out-of-position,airbag apparatus which effectively restrain the occupant regardless ofthe occupant's position are advantageous.

During a front end collision with a standard airbag, if the occupant isrestrained by a seat belt, the occupant's upper torso bends at the waistand hits the primary airbag. However, depending on the design of thevehicle seat and force of the collision, there is a tendency for anoccupant to slide forward along the seat and slip below the primaryairbag, sometimes even entering into leg compartment of the vehicle.Alternatively, the legs and knees of the occupant may slide or shift toone side of the seat or the other. The tendency is pronounced when theoccupant is not properly restrained by a seat belt. This tendency may bereferred to as “submarining”. Submarining often causes the occupant'supper torso to bend at the waist but not in a direction perpendicular tothe primary airbag. When the occupant submarines, the primary airbag isless effective in protecting the occupant.

Submarining is more prevalent in vehicles which have large leg roomcompartments. Vehicles which have restricted leg room, such as sportscars, have a lower submarining tendency. In vehicles like sports cars,the distance between the legs and knees of the occupant and theinstrument panel is shorter than the distance in vehicles such as sportutility vehicles or trucks. In an accident in a sports car, the knees ofthe occupant often strike the instrument panel. The instrument panelthen prevents submarining. Generally, the material of the sports carinstrument panel deforms to some degree to help protect the legs andknees of the occupant. The area of the instrument panel which isimpacted is called the knee bolster.

In order to prevent submarining in vehicles with large leg roomcompartments, a knee airbag system is sometimes used. A knee airbagsystem is generally positioned in the lower portion of the instrumentpanel. Knee airbag systems allow vehicle manufacturers to designvehicles with more leg room and still have safety comparable to that ofvehicles with less leg room.

The knee airbag system includes an inflator, a housing, an airbag, and atrim cover panel. The housing is a conventional enclosure for securingthe knee airbag components to the vehicle. The housing stores the kneeairbag system components while the airbag is deflated and not in use.

The airbag provides the main structure for protecting the occupant. Thebag is generally made of flexible fabric material. The material isgenerally a weave of NYLON® and/or polyester. Generally, multiple piecesof fabric are sewn together to form an airbag. Alternatively, thematerial may be woven to create a one piece airbag. Preferably, astaught herein, the airbag is formed into cells and made from plasticfilm.

The trim cover panel is a panel which covers the airbag and inflatorwithin the housing and presents an aesthetic trim surface to the vehicleoccupant. The trim cover panel is connected to the housing such that thepressure of the inflating airbag pushes the trim cover panel out of theway.

The inflator, once triggered, uses compressed gas, solid fuel, or acombination to produce rapidly expanding gas to inflate the airbag. Aswith conventional airbag systems, a knee airbag can be a large textilebag which the gas inflates like a balloon. The conventional prior artinflated knee airbag occupies some of the volume of the vehicle legcompartment. The knee airbag system may also include a fixed panel,called a load distribution panel or knee bolster panel. This panel canbe made of foam and hard plastic surrounding a metal substrate. Thispanel can provide support to prevent submarining.

Generally, two designs are used in knee airbag systems. The first designconcentrates on moving a piece of rigid material, similar to thematerial of the instrument panel in a sports car, close to theoccupant's knees and legs thereby creating leg and knee support. This isknown as a load distribution plate. The second design does not use asupport plate. This design relies on the knee airbag to provide thenecessary knee and leg support. Traditional designs of the knee airbagwithout the load distribution plate have been less successful inpreventing submarining. This is due to the fact that the airbag onlypartially fills the volume surrounding the knees and legs of theoccupant and thus the airbag can easily deform and provides lesssupport. On the other hand, it is possible for the knees of the occupantto slip off of the load distribution plate thereby defeating itspurpose. Also, if the load distribution plate is at a significantdistance from the occupant's knees, the occupant can attain asignificant velocity before striking the plate resulting in knee andfemur injuries.

These problems are generally solved by the cellular knee bolster designdescribed in detail herein.

It is known in the art to make an inflatable fabric single chamber kneebolster airbag without a load distribution panel. U.S. Pat. No.3,642,303 and U.S. Pat. No. 5,240,283 are two of many such patents. Itis also known to use an airbag to move a load distribution panel closerto the occupant (see, e.g., U.S. Pat. No. 6,345,838, U.S. Pat. No.6,471,242 and European Patent EP00684164B1).

U.S. Pat. No. 4,360,223 (Kirchoff) describes a low-mount, airbag modulefor the passenger side of an automobile that uses two bags that arefolded within a housing that is open at one end. One of the bags is forrestraining the knees of the passenger to prevent forward sliding in theevent of a crash, the other bag is for restraining the torso. The kneebag is inside the torso bag and they are both attached directly to theinflator, the knee bag being arranged to be inflated first. The torsobag then is inflated to prevent forward rotation of the passenger fromthe hips.

Further, in accordance with Kirchoff, a pressure responsive orifice isprovided in a second opening in the wall of the knee bag. This orificecontrols the flow of gas through the opening in the wall of the knee bagthereby to insure a predetermined gas pressure within the knee bag,while permitting subsequent inflation of the torso bag by gases passinginto the torso bag through the orifice. Thus, a knee bolster airbag isdescribed but it is positioned inside of the main torso airbag andinflated by the same inflator.

U.S. Pat. No. 5,458,366 describes a compartmentalized airbag thatfunctions to move a knee bolster or load distribution plate to the kneesof the occupant. The occupant's knees do not contact directly thecompartmentalized airbag as is in a preferred embodiment of theinvention as described herein below. The '366 patent correctly pointsout that a knee bolster airbag, referred to in the '366 patent as areactive type knee bolster, functions on the principle of a singlecompartment airbag and has the disadvantage that on impact of the kneeswith the airbag, the airbag loses rigidity in the impact area. This isdue to the gas flowing from the impact area to other parts of theairbag.

U.S. Pat. No. 6,092,836 also describes an airbag that moves a loaddistribution plate toward the occupant's knees. This patent points outthat using known knee bolsters, the knees of an improperly seatedoccupant can slide off the knee bolster potentially increasing thetendency of the occupant to submarine under the instrument panel. It isimportant that the knee bolster capture the knees to prevent thisproblem, as is an object of the present invention.

Another problem pointed out by the '836 patent is the tendency, due tothe point loading, for the knees in many airbag knee bolsters topenetrate too far into the bolster and therefore lose some of the energyabsorbing effects. Thus, most knee bolsters use a load distributionplate for the contact point with the occupant's knees. This will also beaddressed in the description of the invention below.

U.S. Pat. No. 6,170,871 describes an unworkable elastic film airbag as aknee bolster. The fact that an elastic film is used results in the airflowing from the point of contact to another unloaded section which thenexpands as a balloon. There is also a danger that if punctured, the '871knee bolster will pop as a balloon since it will not exhibit blunting asdescribed below. One properly designed film knee bolster, as disclosedbelow, makes use of a laminated film material including a layer of ahigh modulus of elasticity film with one or more layers of film having alow elastic modulus. The combination does not expand as a balloon as inthe case of the '871 patent and thus its shape is accurately controlled.Also, if it should get punctured, the hole or tear does not propagate.

U.S. Pat. No. 6,336,653 (Yaniv et al.) describes an inflatable tubularbolster that is meant to reduce leg and knee injuries and prevent theoccupant from submarining under the instrument panel. This designsuffers from the tendency of the occupant's knees to slide off of thebolster if the accident is from an angle or if the occupant is notproperly seated.

US20020149187 (Holtz et al.) describes a soft knee bolster which isbasically composed of cells of fabric airbag material positioned infront of a load distribution plate. The knee bolster of the presentinvention also provides for a soft knee bolster but usually does notrequire a special load distribution or reaction plate. This patentapplication correctly points out that, it would advance the art toprovide a soft-surface inflatable knee bolster airbag system whichprevents submarining while providing a soft surface for contacting avehicle occupant's legs and knees. It would be another advancement inthe art to provide a soft-surface inflatable knee bolster airbag systemwhich functions even though the occupant's legs and knees are“out-of-position”. A further advancement in the art would be to providea soft-surface inflatable knee bolster airbag system which is compact,simple, and has fewer parts. The present invention provides theseadvancements in a novel and useful way. All of these advancements areavailable in the cellular bolster as first described in the currentassignee's U.S. Pat. No. 5,505,485.

U.S. Pat. No. 6,685,217 describes a flat mattress like airbag, similarto those disclosed in assignee's prior patents, for use as a kneerestraint.

1.5 Ceiling Deployed Airbags

U.S. Pat. No. 5,322,326 (Ohm) describes a small, limited protectionairbag manufactured in Korea. Although not disclosed in the patent, itappears to use a plastic film airbag material made from polyurethane. Itis a small airbag and does not meet U.S. standards for occupantprotection (FMVSS-208). The film has a uniform thickness and if scaledto the size necessary for meeting U.S. standards, it would likely becomeof comparable thickness and weight as the current fabric airbags.

Of particular interest, FIG. 6 shows an airbag having a shape thatconforms to the human body by forming a two-fold pocket bag. Junctionpoints are provided such that after inflation, the head of a passengeris protected by an inflated part around the upper junction point whilethe upper part of the passenger is covered with the other inflated partaround the middle junction points and a U-shaped junction line. Incontrast to some pertinent inventions disclosed below, the junctionpoints and lines do not enable the formation of an airbag having aplurality of substantially straight or elongate compartments, or even amultiplicity of cells, which can be deployed along the side of a vehiclein order to protect the occupant(s) from injury. Rather, the junctionpoints and lines result in the formation of a limited-use airbag whichwill conform only to the human body, i.e., having a section for engagingthe head and a section for engaging the upper body. Other applicationsof junction points and lines are not contemplated by Ohm.

1.5.1 Side Curtain Airbags

U.S. Pat. No. 5,439,247 describes a fabric hose and quilt-type airbagthat is meant to protect front seat occupants in side impacts. Theconstruction has a rectangular peripheral tube with an inner sectionformed by stitching the fabric together to form cells or tubes. Asidefrom the fact that this is made from fabric, there is no discussion asto how this airbag is supported during a crash and it appears likelythat the bag will be pushed out the window by the head of the occupant.Although it is mentioned that the airbag can be deployed from either thedoor or the ceiling, it does not extend into the rear section of thevehicle passenger compartment. There appears to be no prior art sidecurtain airbags made from fabric that predate the disclosure in thecurrent assignee's patents listed above. There also is no prior art formaking a side curtain airbag from plastic film.

U.S. Pat. No. 6,457,745 (Heigl) describes how to achieve the effects oftethers without actually having them. In this case, loose threads areused as if they were a seam to permit the weaving of a fabric airbag andat the same time to achieve control over the shape of the resultingairbag. In particular, for side curtain airbags, it can be desirable tohave a roughly uniform thickness across the entire front and rear seatspan except where the seat back would interfere. However, to achievethis ideal would require many tethers since left to its own, the airbagswould tend to form spherical-like chambers. As stated in the currentassignee's patents on film airbags, this is by nature less of a problemwith film since the tendency of inelastic film is to form ellipsoidsrather than spheres which is the tendency of fabric. However, this isnot the only advantage of film in this arena as will be seen below.Since sheets of plastic film can be easily manufactured in any thicknessand since they can be easily joined using either heat or adhesivesealing, the opportunities for controlling film geometry greatly exceedthat of fabric. Thus, by practicing the teachings of this invention,very substantial benefits accrue, as will be shown below.

1.5.2 Frontal Curtain Airbags

With the exception of U.S. Pat. No. 5,322,326 discussed above, thereappears to be little if any other prior art on ceiling-mounted airbagsfor frontal crash protection and none whatsoever that extend so as tooffer protection for multiple occupants.

1.5.3 Other Compartmentalized Airbags

U.S. Pat. No. 3,511,519 (Martin) describes a large fabric airbag whichis shown impacting the occupant. It does not discuss the problem ofinjury to the occupants due to the impact of the airbag which wouldcertainly be the case with this design.

U.S. Pat. No. 4,262,931 (Strasser) describes two airbags joined togetherto cover right and center seating positions. These airbags are notmounted on the vehicle ceiling.

U.S. Pat. No. 3,638,755 (Sack) describes a two-bag airbag combination,however, one bag is contained within the other.

U.S. Pat. No. 3,752,501 (Daniel) describes an inflatable cushion devicefor protective interposition between a vehicle operator and the rim andhub of a vehicle steering wheel assembly. The cushion is compartmentedto provide, when inflated, peripheral ring compartmentation injuxtaposition to the steering wheel rim and center compartmentation inoverlying juxtaposition to the steering wheel hub. The peripheral ringcompartmentation, when pressurized, provides greater resistance tocollapse than the center compartmentation, whereby the peripheral ringcompartmentation is adapted to guide the vehicle operator upon contactof the latter with the cushion toward the center compartmentationthereby maintaining the vehicle operator in substantially centeredcushioned relationship to the steering wheel assembly under vehicleimpact conditions. This airbag contains two compartments; an outer,donut-shaped ring or torus, and an inner compartment of somewhat largervolume. This is an example of a bag within a bag where an outer bag isconnected to an inner bag by flapper valves.

U.S. Pat. No. 4,227,717 (Bouvier) describes a method for protecting amotorcycle operator with a plurality of tubular plastic or fabricairbags. These tubes deploy upward from a housing mounted on themotorcycle.

1.6 Rear-of-Seat Mounted Airbags

There is little, if any, prior art for rear-of-seat mounted airbags ofthe type described herein.

1.7 Exterior Airbags

There is little, if any, prior art for exterior mounted airbags madefrom plastic film.

1.8 Variable Vent

U.S. Pat. No. 3,573,885 (Brawn) describes a blowout patch assembly butnot variable exhaust orifices.

U.S. Pat. No. 3,820,814 (Allgaier) describes variable exhaust ventslocated within the fabric airbag material.

U.S. Pat. No. 3,888,504 (Bonn) describes an inflatable occupantrestraint airbag which is comprised at least in part of a woven stretchfabric which is permeable to fluid used to inflate the bag, the baghaving a variable porosity which increases and decreases in relation tothe fluid pressure within the bag.

U.S. Pat. No. 4,394,033 (Goetz) describes a temperature compensationsystem. The inflatable occupant-restraint system in a vehicle includes agenerator for producing fluid under pressure placed such that a portionof the generator is outside the cushion and has a resilient ventingstructure for dumping increasing fractions of gas volume outside thecushion at increasing operating temperatures.

U.S. Pat. No. 4,805,930 (Takada) describes another temperaturecompensation system. Further, it describes stitched thread seams betweenfabric elements of the envelope of a vehicle safety airbag which inducelocalized distension and opening up of the envelope fabrics along theseams, thereby causing the film coatings of the envelope fabric torupture along the seam and allow gas to escape and maintain asubstantially constant overall maximum pressure, regardless ofvariations in ambient temperature.

U.S. Pat. No. 3,675,942 (Huber) describes a unidirectional valve whichpermits air to enter the bag, but prevents its escape in the event thepressure within the bag exceeds that of the atmosphere within thevehicle, such as by the impact of a person with the bag.

U.S. Pat. No. 4,964,652 (Karlow) describes a system for ventingexcessively high pressure gas incident to deployment of an airbagincluding a diaphragm that is rupturable upon the occurrence of athreshold pressure internally of the airbag to instantaneously releasethe pressure. This is a pressure relief system through the center of themodule.

1.8.1 Discharge Valves for Airbags

Prior art valves for possible use with airbags includes those describedin U.S. Pat. No. 4,719,943 (Perach), and U.S. Pat. No. 5,855,228(Perach).

Also, U.S. Pat. No. 5,653,464 (Breed et al.) discloses a variable venthole for an airbag (FIGS. 7 and 7A). The variable vent is formed in aseam of the airbag and includes a hinged elastic member biased so thatit tends to maintain the vent in a closed position. As pressure rises inthe airbag, the vent is forced open. The vent contains an opening formedbetween a film layer of the airbag and a reinforcement member. The filmlayer is also sealed to the reinforcing member

Flow of gas out of an airbag may be controlled during inflation anddeflation of the airbag based on the morphology of the occupant for whomdeployment of the airbag will be effective as disclosed in U.S. Pat. No.5,822,707 (Breed et al.). This patent, as well as others assigned to thecurrent assignee, further describes that gas outflow may also becontrolled based on other properties of the occupant to be protected bythe deploying airbag including but not limited to the occupant'sposition, identification and/or type.

1.9 Airbags with a Barrier Coating

Barrier coatings which prevent, or reduce, contact of a selectedsubstrate with a gas, vapor, chemical and/or aroma have been widelydescribed. A recent improvement in barrier coatings is described in U.S.Pat. No. 6,087,016 and U.S. Pat. No. 6,232,389.

To date, barrier coatings have not been commercially applied in airbagsmade of fabric and in particular side curtain airbags made of fabricwhich is often permeable. It would thus be desirable to improve theimpermeability of the fabric of the airbags.

In contrast to frontal impact driver and passenger airbags which onlyare required to retain the inflation gas or other fluid for typically afraction of a second, the side curtain airbag must retain the inflationfluid for several seconds in order to offer protection for rolloverevents, for example. Also, the side curtain or ceiling-mounted airbagmust deploy rapidly and pack into a small space.

It is disadvantageous that current polymer coatings used on such airbagsare relatively thick thereby increasing the mass of the airbag making itdifficult to pack into a ceiling space and delay the deployment of theairbag in an accident, thereby increasing the chance that an occupantwill not receive the full benefit of the airbag. As a result of thesedisadvantages, such coatings are not optimal for use on side curtainairbags.

Much of the leakage in side curtain airbags occurs through the seamswhere the front and rear panels forming the side curtain airbag arejoined. This is due to the methods of joining such panels which includesewing and interweaving. Thus, although the barrier coatings of thisinvention will reduce the leakage through the panel surfaces, and reducethe cost and mass of the airbag, alternative treatments for the seamarea are also desirable as described and disclosed herein.

2. Definitions

“Pattern recognition” as used herein will generally mean any systemwhich processes a signal that is generated by an object (e.g.,representative of a pattern of returned or received impulses, waves orother physical property specific to and/or characteristic of and/orrepresentative of that object) or is modified by interacting with anobject, in order to determine to which one of a set of classes that theobject belongs. Such a system might determine only that the object is oris not a member of one specified class, or it might attempt to assignthe object to one of a larger set of specified classes, or find that itis not a member of any of the classes in the set. The object can also bea vehicle with an accelerometer that generates a signal based on thedeceleration of the vehicle. Such a system might determine only that theobject is or is not a member of one specified class (e.g.,airbag-required crashes), or it might attempt to assign the object toone of a larger set of specified classes, or find that it is not amember of any of the classes in the set. One such class might consist ofvehicles undergoing a crash of a certain severity into a pole. Thesignals processed are generally a series of electrical signals comingfrom transducers that are sensitive to acoustic (ultrasonic) orelectromagnetic radiation (e.g., visible light, infrared radiation,capacitance or electric and/or magnetic fields), although other sourcesof information are frequently included. Pattern recognition systemsgenerally involve the creation of a set of rules that permit the patternto be recognized. These rules can be created by fuzzy logic systems,statistical correlations, or through sensor fusion methodologies as wellas by trained pattern recognition systems such as neural networks,combination neural networks, cellular neural networks or support vectormachines or a neural computer.

A trainable or a trained pattern recognition system as used hereingenerally means a pattern recognition system that is taught to recognizevarious patterns constituted within the signals by subjecting the systemto a variety of examples. The most successful such system is the neuralnetwork used either singly or as a combination of neural networks. Thus,to generate the pattern recognition algorithm, test data is firstobtained which constitutes a plurality of sets of returned waves, orwave patterns, or other information radiated or obtained from an object(or from the space in which the object will be situated in the passengercompartment, i.e., the space above the seat) and an indication of theidentity of that object. A number of different objects, optionally indifferent positions, are tested to obtain the unique patterns from eachobject. As such, the algorithm is generated, and stored in a computerprocessor, and which can later be applied to provide the identity of anobject based on the wave pattern, for example, received during use by areceiver connected to the processor and other information. For thepurposes here, the identity of an object sometimes applies to not onlythe object itself but also to its location and/or orientation in thepassenger compartment. For example, a rear-facing child seat is adifferent object than a forward-facing child seat and an out-of-positionadult can be a different object than a normally-seated adult. Not allpattern recognition systems are trained systems and not all trainedsystems are neural networks. Other pattern recognition systems are basedon fuzzy logic, sensor fusion, Kalman filters, correlation as well aslinear and non-linear regression. Still other pattern recognitionsystems are hybrids of more than one system such as neural-fuzzysystems.

The use of pattern recognition, or more particularly how it is used, isimportant to some of the inventions disclosed herein. In the above-citedprior art, except the current assignee's, pattern recognition which isbased on training, as exemplified through the use of neural networks, isnot mentioned for use in monitoring the interior passenger compartmentor exterior environments of the vehicle in all of the aspects of theinvention disclosed herein. Thus, the methods used to adapt such systemsto a vehicle are also not mentioned.

A “pattern recognition algorithm” will thus generally mean an algorithmapplying or obtained using any type of pattern recognition system, e.g.,a neural network, sensor fusion, fuzzy logic, etc.

To “identify” as used herein will generally mean to determine that theobject belongs to a particular set or class. The class may be onecontaining, for example, all rear facing child seats, one containing allhuman occupants, or all human occupants not sitting in a rear facingchild seat, or all humans in a certain height or weight range dependingon the purpose of the system. In the case where a particular person isto be recognized, the set or class will contain only a single element,i.e., the person to be recognized. The class may also be one containingall frontal impact airbag-desired crashes into a pole at 20 mph, onecontaining all events where the airbag is not required, or onecontaining all events requiring a triggering of both stages of a dualstage gas generator with a 15 millisecond delay between the triggeringof the first and second stages.

To “ascertain the identity of” as used herein with reference to anobject will generally mean to determine the type or nature of the object(obtain information as to what the object is), i.e., that the object isan adult, an occupied rear-facing child seat, an occupied front-facingchild seat, an unoccupied rear-facing child seat, an unoccupiedfront-facing child seat, a child, a dog, a bag of groceries, a car, atruck, a tree, a pedestrian, a deer etc.

An “object” in a vehicle or an “occupying item” of a seat may be aliving occupant such as a human or a dog, another living organism suchas a plant, or an inanimate object such as a box or bag of groceries oran empty child seat.

A “rear seat” of a vehicle as used herein will generally mean any seatbehind the front seat on which a driver sits. Thus, in minivans or otherlarge vehicles where there are more than two rows of seats, each row ofseats behind the driver is considered a rear seat and thus there may bemore than one “rear seat” in such vehicles. The space behind the frontseat includes any number of such rear seats as well as any trunk spacesor other rear areas such as are present in station wagons.

An “optical image” will generally mean any type of image obtained usingelectromagnetic radiation including visual, infrared, terahertz andradar radiation.

In the description herein on anticipatory sensing, the term“approaching” when used in connection with the mention of an object orvehicle approaching another will usually mean the relative motion of theobject toward the vehicle having the anticipatory sensor system. Thus,in a side impact with a tree, the tree will be considered as approachingthe side of the vehicle and impacting the vehicle. In other words, thecoordinate system used in general will be a coordinate system residingin the target vehicle. The “target” vehicle is the vehicle that is beingimpacted. This convention permits a general description to cover all ofthe cases such as where (i) a moving vehicle impacts into the side of astationary vehicle, (ii) where both vehicles are moving when theyimpact, or (iii) where a vehicle is moving sideways into a stationaryvehicle, tree or wall.

“Out-of-position” as used for an occupant will generally mean that theoccupant, either the driver or a passenger, is sufficiently close to anoccupant protection apparatus (airbag) prior to deployment that he orshe is likely to be more seriously injured by the deployment eventitself than by the accident. It may also mean that the occupant is notpositioned appropriately in order to attain the beneficial, restrainingeffects of the deployment of the airbag. As for the occupant being tooclose to the airbag, this typically occurs when the occupant's head orchest is closer than some distance such as about 5 inches from thedeployment door of the airbag module. The actual distance where airbagdeployment should be suppressed depends on the design of the airbagmodule and is typically farther for the passenger airbag than for thedriver airbag.

“Transducer” or “transceiver” as used herein will generally mean thecombination of a transmitter and a receiver. In some cases, the samedevice will serve both as the transmitter and receiver while in others,two separate devices adjacent to each other will be used. In some cases,a transmitter is not used and in such cases, transducer will mean only areceiver. Transducers include, for example, capacitive, inductive,ultrasonic, electromagnetic (antenna, CCD, CMOS arrays), electric field,weight measuring or sensing devices. In some cases, a transducer maycomprise two parts such as the plates of a capacitor or the antennas ofan electric field sensor. Sometimes, one antenna or plate willcommunicate with several other antennas or plates and thus for thepurposes herein, a transducer will be broadly defined to refer, in mostcases, to any one of the plates of a capacitor or antennas of a fieldsensor and in some other cases, a pair of such plates or antennas willcomprise a transducer as determined by the context in which the term isused.

For the purposes herein, a “neural network” is defined to include allsuch learning systems including cellular neural networks, support vectormachines and other kernel-based learning systems and methods, cellularautomata and all other pattern recognition methods and systems thatlearn. A “combination neural network” as used herein will generallyapply to any combination of two or more neural networks or otherprocessing units as most broadly defined that are either connectedtogether or that analyze all or a portion of the input data. Typically,it is a system wherein the data to be processed is separated intodiscrete values which are then operated on and combined in at least atwo stage process and where the operation performed on the data at eachstage is, in general, different for each discrete value and where theoperation performed is at least determined through a training process.It includes ensemble, modular, cellular neural networks, among others,and support vector machines and combination neural networks.

A “neural computer” is a computer designed to efficiently execute one ormore neural networks primarily in hardware. Thus, it is typically mustfaster than a microprocessor running a neural network algorithm.

A “sensor” as used herein is generally a combination of two transducers(a transmitter and a receiver) or one transducer which can both transmitand receive. In some cases it may refer to a single receiver such as atemperature sensor or passive infrared sensor.

The “headliner” is the trim which provides the interior surface to theroof of the vehicle.

A “sensor system” includes any of the sensors listed above in thedefinition of “sensor” as well as any type of component or assembly ofcomponents that detect, sense or measure something.

An “occupant protection system” or “occupant protection apparatus” isany device, apparatus, system or component which is actuatable ordeployable or includes a component which is actuatable or deployable forthe purpose of attempting to reduce injury to the occupant in the eventof a crash, rollover or other potential injurious event involving avehicle.

An “occupant restraint device” includes any type of device that isdeployable in the event of a crash involving the vehicle for the purposeof protecting an occupant from the effects of the crash and/orminimizing the potential injury to the occupant. Occupant restraintdevices thus include frontal airbags, side airbags, seatbelt tensioners,nets, knee bolsters, side curtain airbags, externally deployable airbagsand the like.

A diagnosis of the “state of the vehicle” means a diagnosis of thecondition of the vehicle with respect to its stability and properrunning and operating condition. Thus, the state of the vehicle could benormal when the vehicle is operating properly on a highway or abnormalwhen, for example, the vehicle is experiencing excessive angularinclination (e.g., two wheels are off the ground and the vehicle isabout to rollover), the vehicle is experiencing a crash, the vehicle isskidding, and other similar situations. A diagnosis of the state of thevehicle could also be an indication that one of the parts of thevehicle, e.g., a component, system or subsystem, is operatingabnormally.

A “part” of the vehicle includes any component, sensor, system orsubsystem of the vehicle such as the steering system, braking system,throttle system, navigation system, airbag system, seatbelt retractor,airbag inflation valve, airbag inflation controller and airbag ventvalve, as well as those listed below in the definitions of “component”and “sensor”.

The crush sensing zone is that portion of the vehicle that has crushedat the time that the crash sensor must trigger deployment of therestraint system.

The term “airbag” is often used to mean all deployable passive passengerprotective devices including airbags, seatbelts with pretensioners anddeployable nets.

The “A-pillar” of a vehicle and specifically of an automobile is definedas the first roof supporting pillar from the front of the vehicle andusually supports the front door. It is also known as the hinge pillar.

The “B-Pillar” is the next roof support pillar rearward from theA-Pillar.

The “C-Pillar” is the final roof support usually at or behind the rearseats

The term “squib” represents the entire class of electrically initiatedpyrotechnic devices capable of releasing sufficient energy to cause avehicle window to break. It is also used to represent the mechanismwhich starts the burning of an initiator which in turn ignites thepropellant within an inflator. Squib generally refers to electricalinitiation while primer is usually used for mechanical initiationhowever these terms are frequently used interchangeably and thus eitherwill mean the device that initiates airbag deployment whether byelectrical or mechanical means.

The term “airbag module” generally connotes a unit having at least oneairbag, a gas generator for producing a gas, an attachment or couplingstructure for attaching the airbag(s) to and in fluid communication withthe gas generator so that gas is directed from the gas generator intothe airbag(s) to inflate the same, an initiator for initiating the gasgenerator in response to a crash of the vehicle for which deployment ofthe airbag is desired and structure for attaching or connecting the unitto the vehicle in a position in which the deploying airbag(s) will beeffective in the passenger compartment of the vehicle. In the instantinvention, the airbag module may also include occupant sensingcomponents, diagnostic and power supply electronics and componentrywhich are either within or proximate to the module housing.

The term “occupant protection device” as used herein generally includesany type of device which is deployable in the event of a crash involvingthe vehicle for the purpose of protecting an occupant from the effectsof the crash and/or minimizing the potential injury to the occupant.Occupant protection devices thus include frontal airbags, side airbags,seatbelt tensioners, knee bolsters, side curtain airbags, deployablenets, externally deployable airbags and the like.

A “composite airbag” is any airbag comprised of a film and a fabric, twoor more films, a film and a net or other combination of two or morematerials or layers such that each material contributes to thestructural or tear properties of the composite. This is in contrast tothe combinations of a film and fabric used previously in neoprene orsilicone coated fabric airbags in that, in the prior art cases, thecoating does not materially effect either the elastic modulus,stiffness, strength or tear resistance of the airbag where in the caseof the composite airbag disclosed herein, the film contributessignificantly to one or more of these properties. Note that the two ormore layers may or may not be joined together including cases where thelayers are joined during an extrusion processing step such as inco-extrusion, by a casting process, progressive coating process, orwhere a film layer is combined with another reinforcing material such asfibers or a woven or molded net in addition to the most common method ofjoining layers by adhesive.

The following definitions related to coatings are generally taken fromU.S. Pat. No. 6,087,016 and U.S. Pat. No. 6,232,389. As used herein, theterm “mixture” or “coating mixture” is interpreted to include trueliquid solutions, as well as colloidal dispersions, suspensions,emulsions and latexes as they are conventionally defined. For example,by “colloidal dispersion or latex”, it is meant any dispersion orsuspension of particles in liquid, the particles being of a size greaterthan molecular scale, e.g., about 0.001 to about 0.1 micron. An emulsiongenerally contains particles of about 0.05 to 1.0 microns, in liquid. A“suspension” generally contains particles of greater than 1.0 micron inliquid.

A “barrier coating mixture” as used herein means a liquid containingdissolved or suspended solids, which is used to apply the solids to asubstrate. A novel aspect of one of the present inventions is that thebarrier coating mixtures provide a better dispersion of platelet fillersin liquid at an unusually low solids content, e.g., between about 1% toabout 30% solids as described in more detail below. According to thisinvention, once the “coating mixture” is dried, it is referred to as a“dried coating” or a “film”. The term “vapor barrier” implies a barrierto a liquid and its vapor. Conventionally, a vapor is the gas inequilibrium with a liquid at atmospheric pressure. For simplicity, asused herein, the term “vapor barrier” can be interpreted to mean abarrier to gases and chemicals as well as traditionally defined vapors,as well as a barrier to moisture, generally water or water vapor.

The term “gas barrier” includes a barrier to oxygen, nitrogen, carbondioxide and other gases. The term “chemical barrier” includes a barrierto the migration or blooming of a molecule from one substrate to anotheror out of one substrate to that substrate's surface.

The term “aspect ratio” is a characteristic of every platelet materialin solid form. Aspect ratio is a lateral dimension of a platelet fillerparticle, e.g., mica flake, divided by the thickness of the platelet.The term “high aspect ratio” refers to a platelet filler whose lateraldimension divided by thickness is greater than 25. The aspect ratio ofany filler is an inherent property of the selected filler. For example,MICROLITE® 963++aqueous vermiculite solution [W. R. Grace] has acharacteristic aspect ratio of about 10,000 or dimensions of 10-30 μm×10Å.

Intercalation is defined as the state of a coating composition in whichpolymer is present between each layer of a platelet filler.Intercalation can be defined by the detection of an X-ray line,indicating a larger spacing between vermiculite layers than in theoriginal mineral. The term “exfoliation” is defined for layered fillersas the complete separation of individual layers of the originalparticle, so that polymer completely surrounds each particle.Preferably, so much polymer is present between each platelet, that theplatelets are randomly spaced. No X-ray line appears because of therandom spacing of exfoliated platelets. In some circumstances, thefiller can exfoliate when dispersed in an aqueous or non-aqueous medium.This would result in a higher aspect ratio than that of a solid particlebefore dispersion.

The term “effective aspect ratio” relates to the behavior of theplatelet filler when incorporated into a binder. The platelet may notexist in a single platelet formation, but in many forms, such as abundle of 10-50 platelets or hundreds of platelets, referred to asagglomerates. If the platelets are not in the single layer form, theaspect ratio of the entire bundle or agglomerate is much lower than thatof the single layer particle. Therefore, the aspect ratio of theparticles in a binder is referred to as an effective aspect ratio. Theeffective aspect ratio is determined by plotting the experimental dataversus theoretical model, such as described by E. L. Cussler et al, J.Membrane Sci., 38: 161-174 (1988). A graph of reduction in permeabilityversus the volume % of filler in the binder generates theoretical curvesfor each effective aspect ratio. The graph predicts an effective aspectratio for the experimental data (see FIG. 43).

It is important in the understanding of the effects of the coatings ofthis invention to differentiate between “effective aspect ratio” and“aspect ratio”. The aspect ratio is characteristic of a plateletmaterial in the solid form or one platelet and can be determined bylight scattering techniques or microscopy. The term “effective aspectratio” is much different in that it relates to the behavior of theplatelet when incorporated into a binder. It may no longer be a singleplatelet but instead bundles of platelets referred to as agglomerates.This value is determined using experimental permeability data plottedversus theoretical behavior of the platelet. For example, experimentaldata when plotted versus the theoretical model of the platelet in thebinder [see E. L. Cussler et al, J. Membrane S., 38:161-174 (1988)] isdirectly related to the barrier improvement of the coating throughCussler's theoretical model. Most commercially available fillers haveaspect ratios ranging from 25 up to 10,000. However, the effectiveaspect ratio of these fillers is much lower when incorporated into abinder and is directly related to the barrier improvement due to theplatelet filler, generally resulting in reduced barrier properties. Itis important to distinguish between these terms for barrier coatingscontaining platelet fillers.

Much of the disclosure herein involving particular barrier coatings isbased on U.S. Pat. No. 6,087,016 and U.S. Pat. No. 6,232,389. However,the invention is not limited to airbags including the barrier coatingsdescribed in these patents and encompasses airbags including anycomparable barrier coatings and any barrier coatings encompassed by theclaims.

Preferred embodiments of the invention are described below and unlessspecifically noted, it is the applicant's intention that the words andphrases in the specification and claims be given the ordinary andaccustomed meaning to those of ordinary skill in the applicable art(s).If applicant intends any other meaning, he will specifically state he isapplying a special meaning to a word or phrase.

Likewise, applicant's use of the word “function” here is not intended toindicate that the applicant seeks to invoke the special provisions of 35U.S.C. § 112, sixth paragraph, to define his invention. To the contrary,if applicant wishes to invoke the provisions of 35 U.S.C.§112, sixthparagraph, to define his invention, he will specifically set forth inthe claims the phrases “means for” or “step for” and a function, withoutalso reciting in that phrase any structure, material or act in supportof the function. Moreover, even if applicant invokes the provisions of35 U.S.C. § 112, sixth paragraph, to define his invention, it is theapplicant's intention that his inventions not be limited to the specificstructure, material or acts that are described in the preferredembodiments herein. Rather, if applicant claims his inventions byspecifically invoking the provisions of 35 U.S.C. § 112, sixthparagraph, it is nonetheless his intention to cover and include any andall structure, materials or acts that perform the claimed function,along with any and all known or later developed equivalent structures,materials or acts for performing the claimed function.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system forsubstantially filling a passenger compartment of a vehicle with airbagsto protect an occupant during a crash involving the vehicle. Otherpossible objects are set forth in the parent applications.

In order to achieve this object, an airbag deployment system for avehicle having a passenger compartment in accordance with the inventionincludes a plurality of airbags arranged to substantially fill thepassenger compartment upon deployment, an inflator system for inflatingthe airbags and a crash sensor system coupled to the inflator system fordirecting the inflator system to inflate the airbag. Multiple housingsmay be arranged around the passenger compartment, each including atleast one airbag. Some of the airbags may be interconnected to provide aprimary airbag and at least one secondary airbag extending from theprimary airbag. The inflator system may be an aspirated inflator system.The crash sensor system may be an anticipatory sensor system. Theairbags may be film airbags. One-way valves may be arranged betweenadjacent airbags.

Further, one embodiment of an airbag for a vehicle in accordance withthe invention includes at least one section of material defining aplurality of cells, chambers or compartments, and one-way valvesarranged in connection with the material section(s) between the cells tocontrol flow of inflating fluid between the cells. Each valve can leadfrom a respective first cell to a respective second cell and arepreferably designed to close once a predetermined pressure prevails inthe second cell to prevent fluid outflow from the respective secondcell.

The cells may be interconnected such that at least one cell isinterposed between and connected to two other cells. A plurality ofvalves may be arranged between adjacent pairs of the cells, or only asingle valve may be arranged between an adjacent pair of cells.

In some embodiments, only one cell is in direct communication with asource of inflating fluid. In this case, if this single cell is a commondistribution manifold, a plurality of cells are directly connected to itvia one-way valves. This provides a distribution from the single commoncell directly to a plurality of other cells, which may not be connectedin turn to other cells via one-way valves. On the other hand, each othercell may be connected to yet another cell to provide one or more seriesof linked cells, each series having three or more cells and originatingfrom the common cell.

An envelope can surround the cells and may be made of, for example,film.

In one operational embodiment of a vehicle including such an airbag, thevehicle includes an instrument panel and a front seat on which anoccupant sits opposite the instrument panel. The airbag has a storageposition in connection with the instrument panel and a deployed positionextending outward from the instrument panel. An inflator inflates theairbag from the storage position to the deployed position. When in thedeployed position, the airbag is arranged in a space between the kneesof the occupant when seated on the front seat and the instrument panel.

Another operational embodiment includes a headliner or ceiling and aseat on which an occupant sits below the headliner or ceiling. Theairbag has a storage position in connection with the headliner orceiling and a deployed position extending outward from the headliner orceiling. An inflator inflates the airbag from the storage position tothe deployed position. When in the deployed position, the airbag isarranged in a space between the occupant when seated on the seat and aside of the vehicle.

An airbag system in accordance with the invention includes an inflatableairbag having a plurality of interconnected chambers (cells orcompartments) and arranged to engage part of a vehicle occupant uponinflation, and an inflator arranged to direct inflating fluid directlyinto only a portion of the chambers of the airbag. The airbag included aplurality of one-way valves arranged between adjacent chambers tocontrol flow of inflating fluid from the inflator to all of the chambersto thereby enable the airbag to be inflated. The chambers areinterconnected such that at least one chamber is interposed between andconnected to two other chambers. Variations to the airbag system includethe variations discussed above. Also, the chambers may include a row ofprimary airbag chambers and at least one secondary airbag chamberextending from each primary airbag chamber.

A motor vehicle in accordance with the invention includes a frameincluding a headliner or ceiling and instrument panel, an airbag devicemounted to the frame and comprising an inflator for providing inflatingfluid upon actuation thereof and a compartmentalized airbag having aplurality of compartments (cells or chambers) in communication with theinflator, and a mounting mechanism for mounting the airbag device to theframe such that the airbag, when inflated, is present in a space betweenthe frame and part of an occupant situated in a seat of the vehicle. Theairbag includes one-way valves arranged between the compartments tocontrol flow of inflating fluid between the compartments. Thecompartments may include a row of primary airbag compartments and atleast one secondary airbag compartment extending from each primaryairbag compartment.

Inflation of the airbag is caused by a determination by a crash sensorsystem of an actual or expected crash involving the vehicle and mayinclude an anticipatory crash sensor which forecasts a crash between thevehicle and another object prior to impact of the vehicle by the otherobject. In this manner, the airbag is inflated prior to the crash.

Various constructions of the airbag are possible, some of which arementioned above. In one construction, the airbag includes at least twopieces of substantially flat inelastic plastic film having peripheraledges, one of which has an inlet port for inflow of inflating fluid, andthe pieces of inelastic plastic film are attached together at least atperipheral edges to form a substantially sealed airbag. The airbag mayhave interconnected chambers formed by attaching the pieces of inelasticplastic film together. In another construction, the airbag includesinelastic plastic film, an inlet port for inflow of inflating fluid anda variable outlet vent which is designed to open variably in response topressure in the airbag. In another construction, the airbag includes asingle piece of inelastic plastic film having an inlet port for inflowof inflating fluid. In yet another construction, the airbag includes anouter airbag made of at least one layer of plastic film and an innerairbag made of at least one layer of plastic film and arranged to fillan interior volume of the outer airbag when inflated.

In still another embodiment, the airbag includes a first sheet of filmand a member arranged in connection therewith for arresting thepropagation of a tear therein. The member may be (a) a network ofmulti-directional material strips; (b) a second sheet of film havingsubstantially anisotropic tear properties with the direction of tearresistance thereof being different than a direction of tear resistanceof the first sheet of film; and (c) a thermoplastic elastomeric materialarranged at specific locations such that the locations are thicker incomparison to an average thickness of the first sheet of film.

In still another embodiment, the airbag includes a composite airbaghaving at least one layer of inelastic plastic film attached to a layerof a more elastic plastic film, the second layer serving to blunt thepropagation of a tear.

In another embodiment, the airbag includes a plurality of materialsections defining a plurality of interconnected cells. In yet anotherembodiment, a net surrounds the airbag during and after deployment ofthe airbag.

The inflator may include a gas generator for producing pressurized gasto inflate the airbag and an aspiration system which combines gas fromthe passenger compartment of the vehicle with pressurized gas from thegas generator and directs the combined flow of gas into the airbag.

A knee bolster airbag system for protecting the knees of an occupant ofa vehicle includes an airbag having a plurality of cells, an inflatorarranged to inflate the airbag and a housing for storing the airbag, thehousing being mounted in the vehicle in a position in which the airbagengages lower extremities of the occupant upon inflation. Preferably,the airbag is dimensioned to occupy a space between the occupant's legsand structural components of an instrument panel of the vehicle wheninflated.

Another knee bolster airbag system for a vehicle includes an airbaghaving a plurality of chambers and an inflator arranged to inflate theairbag such that the airbag engages the lower extremities of a vehicleoccupant upon inflation and distribute impact force imposed by the lowerextremities over the chambers. The airbag provides a soft surfaceadapted to engage the lower extremities of an occupant. Optionally, theairbag is arranged such that when inflated, it occupies a space betweenthe occupant's legs and the vehicle instrument panel such that theinstrument panel provides support for the airbag. In one embodiment, theinflator is arranged to direct gas directly into only a portion of thechambers and the airbag includes a plurality of one-way valves arrangedbetween adjacent chambers to enable flow of gas from the inflator to allof the chambers.

Another vehicle equipped with a knee bolster airbag system in accordancewith the invention includes a compartmentalized airbag knee bolsterdevice mounted to the instrument panel and including an inflator forproviding pressurized gas upon actuation thereof and a compartmentalizedairbag having a plurality of compartments in communication with theinflator. The compartmentalized airbag knee bolster device is mounted tothe instrument panel such that the compartmentalized airbagsubstantially occupies a space between the instrument panel and theknees or lower extremities of an occupant situated in front of theinstrument panel when inflated. The compartmentalized airbag may includea plurality of material sections defining a plurality of compartmentsand one-way valves arranged in the material sections between thecompartments to control flow of inflating fluid between thecompartments. Each compartment can have a width approximately equal toor less than the width of a knee of an occupant of the motor vehicle.

An inflatable tubular bolster for a vehicle in accordance with theinvention includes an inflatable airbag having a plurality of cells, agas generator fluidly connected to the airbag via a gas conduit and acrash sensor connected to the gas generator for detecting an impactinvolving the vehicle. When an impact is detected by the crash sensor,the gas generator causes the cells to be inflated and the airbag deploysfrom a stowed position downward and rearward into a position below aninstrument panel of the vehicle such that it restrains forward anddownward movement of an occupant situated in front of the instrumentpanel. The airbag may be arranged to deploy in front of an occupant'sknees and thereby inhibits forward and downward movement of theoccupant.

A system for protecting occupants of a vehicle during a crash involvingthe vehicle in accordance with the invention includes a plurality ofinflators for generating pressurized gas, a crash sensor system forcontrolling the inflators to begin generating pressurized gas based on acrash involving the vehicle, a plurality of primary airbags eachdirectly connected to a respective inflator and receiving pressurizedgas directly from the respective inflator and at least one secondaryairbag in flow communication with each primary airbag such thatinflation of the primary airbag by the respective inflator causesinflation of the secondary airbag(s). This resembles a chain reaction ofinflating airbags which progresses from an airbag closest to the vehiclestructure inward until contact is made by a secondary airbag with theoccupant. Thus, when a plurality of secondary airbags are present anddistanced sequentially from the primary airbag, gas from the primaryairbag passes into a first one of the secondary airbags and from thefirst secondary airbag to a second one of the secondary airbags and soon. The secondary airbags may include a one-way valve which enables flowof gas from each secondary airbag to an adjoining downstream secondaryairbag. Each primary airbag may also include a one-way valve whichenable flow of gas from the primary airbag to an adjoining secondaryairbag.

In one particular embodiment, the crash system includes an anticipatorycrash sensor arranged to determine whether a crash involving the vehicleis about to occur and to direct the inflators to generate gas prior tothe crash such that the primary airbags and the secondary airbag(s) areinflated prior to the crash. In this manner, substantially the entireunoccupied interior space of the passenger compartment can be filledwith airbags to cushion any occupants in a crash.

Each inflator may include a gas generator for producing pressurized gasto inflate a respective primary airbags and an aspiration system forcombining gas from the passenger compartment of the vehicle withpressurized gas from the gas generator and directing the combined flowof gas into the respective primary airbag.

Other objects and advantages of the present invention will becomeapparent from the following description of the preferred embodimentstaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of embodiments of the inventionand are not meant to limit the scope of the invention as encompassed bythe claims.

FIG. 1 is a perspective view with portions cut away and removed of afilm airbag wherein the film is comprised of at least two layers ofmaterial which have been joined together by a process such asco-extrusion or successive casting or coating.

FIG. 1A is an enlarged view of the inner film airbag layer and outerfilm airbag layer taken within circle 1A of FIG. 1.

FIG. 1B is an enlarged view of the material of the inner film airbag andouter film airbag taken within circle 1A of FIG. 1 but showing analternate configuration where the outer airbag layer has been replacedby a net.

FIG. 1C is an enlarged view of the material of the inner film airbaglayer and outer film airbag layer taken within circle 1A of FIG. 1 butshowing an alternate configuration where fibers of an elastomer areincorporated into an adhesive layer between the two film layers.

FIG. 1D is a perspective view with portions cut away of a vehicleshowing the driver airbag of FIG. 1 mounted on the steering wheel andinflated.

FIG. 2 illustrates a section of a seam area of an airbag showing thedeformation of the elastic sealing film layer.

FIG. 3 is a partial cutaway perspective view of a driver side airbagmade from plastic film.

FIG. 4A is a partial cutaway perspective view of an inflated driver sideairbag made from plastic film and a fabric to produce a hybrid airbag.

FIG. 4B is a partial cutaway perspective view of an inflated driver sideairbag made from plastic film and a net to produce a hybrid airbag.

FIG. 4C is a partial cutaway perspective view of an inflated driver sideairbag made from plastic film having a variable thickness reinforcementin a polar symmetric pattern with the pattern on the inside of theairbag leaving a smooth exterior.

FIG. 4D is an enlarged cross sectional view of the material of the filmairbag taken at 4D-4D of FIG. 4C showing the thickness variation withinthe film material.

FIG. 5A is a partial cutaway perspective view of an inflated driver sideairbag made from plastic film using a blow molding process.

FIG. 5B is a partial cutaway perspective view of an inflated driver sideairbag made from plastic film using a blow molding process so that theairbag design has been partially optimized using finite element airbagmodel where the wrinkles have been eliminated and where the stresseswithin the film are more uniform.

FIG. 5C is a cutaway view of an inflated driver side airbag made fromplastic film showing a method of decreasing the ratio of thickness toeffective diameter.

FIG. 5D is a view of a driver side airbag of FIG. 5C as viewed alongline 5D-5D.

FIG. 6 shows a deployed airbag, supported on the steering wheel of avehicle with a steep steering column, in contact with an occupant.

FIG. 7 shows an inflated airbag and a steering wheel, self-aligned withan occupant.

FIG. 8 shows a driver side airbag module supported by a steering column,but not attached to the steering wheel.

FIG. 9 illustrates an inflated driver side airbag installed on thedashboard of a vehicle.

FIG. 10 shows an airbag system installed on the dashboard of a vehiclewith a vent hole to the engine compartment.

FIGS. 11A and 11B show a tubular inflatable system mounted on thedashboard of a vehicle.

FIG. 12 is a partial cutaway perspective view of a passenger side airbagmade from plastic film.

FIG. 13 is a perspective view with portions cut away of a vehicleshowing the knee bolster airbag or restraint in an inflated conditionmounted to provide protection for front-seated occupants.

FIG. 14 is a perspective view of an airbag and inflator system where theairbag is formed from tubes.

FIG. 15 is a perspective view with portions removed of a vehicle havingseveral deployed film airbags.

FIG. 16 is a view of another preferred embodiment of the invention shownmounted in a manner to provide protection for a front and a rear seatoccupant in side impact collisions and to provide protection againstimpacts to the roof support pillars in angular frontal impacts.

FIG. 16A is a view of the side airbag of FIG. 9 of the side airbag withthe airbag removed from the vehicle.

FIG. 17 is a partial view of the interior driver area of a vehicleshowing a self-contained airbag module containing the film airbag ofthis invention in combination with a stored gas inflator.

FIG. 18 is a view looking toward the rear of the airbag module of FIG.17 with the vehicle removed taken at 18-18 of FIG. 17.

FIG. 18A is a cross sectional view of the airbag module of FIG. 18 takenat 18A-18A.

FIG. 18B is a cross sectional view, with portions cutaway and removed,of the airbag module of FIG. 18 taken at 18B-18B.

FIG. 18C is a cross sectional view of the airbag module of FIG. 18 takenat 18C-18C.

FIG. 18D is a cross sectional view of the airbag module of FIG. 18Ataken at 18D-18D.

FIG. 19 is a perspective view of another preferred embodiment of theinvention shown mounted in a manner to provide protection for a frontand a rear seat occupant in side impact collisions, to provideprotection against impacts to the roof support pillars in angularfrontal impacts and to offer some additional protection against ejectionof the occupant or portions of the occupant.

FIG. 20 is a side view of the interior of a motor vehicle provided withanother form of safety device in accordance with the invention, beforethe safety device moves to the operative state.

FIG. 21 illustrates the vehicle of FIG. 20 when the safety device is inthe operative state.

FIG. 22 is a sectional view of one form of safety device as shown inFIGS. 20 and 21 in a plane perpendicular to the vertical direction.

FIG. 22A is a view as in FIG. 22 with additional sheets of materialattached to span the cells.

FIG. 23 is a side view of the passenger compartment of a vehicle showingthe compartment substantially filled with layers of tubular film airbagssome of which are interconnected.

FIG. 23A is a top view of the airbag arrangement of FIG. 23 taken alongline 23A-23A.

FIG. 24 is a similar but alternate arrangement of FIG. 23.

FIG. 25 is another alternate arrangement to FIG. 23 using airbags thatexpand radially from various inflators.

FIG. 26 is a detail of the radial expanding tubular airbags of FIG. 25.

FIG. 26A is an end view of the airbags of FIG. 26 taken along line26A-26A.

FIG. 27 is a detailed view of a knee bolster arrangement in accordancewith the invention.

FIG. 27A illustrates the deployment stages of the knee bolsterarrangement of FIG. 27.

FIGS. 28A, 28D, 28F, 28H, 28J and 28L illustrate various common fabricairbag designs that have been converted to film and have additional filmlayers on each of the two sides of the airbag.

FIGS. 28B, 28C, 28E, 28G, 28I, 28K and 28M are cross-sectional views ofFIGS. 28A, 28D, 28F, 28H, 28J and 28L.

FIG. 29 is a perspective view of a self limiting airbag system includinga multiplicity of airbags surrounded by a net, most of which has beencutaway and removed, designed to not cause injury to a child in arear-facing child seat.

FIG. 30 is a partial cutaway perspective view of a driver side airbagmade from plastic film having a variable vent in the seam of the airbag.

FIG. 30A is an enlargement of the variable vent of FIG. 30 taken alongline 30A-30A of FIG. 30.

FIG. 31 shows a plot of the chest acceleration of an occupant and theoccupant motion using a conventional airbag.

FIG. 32 shows the chest acceleration of an occupant and the resultingoccupant motion when the variable orifice of this invention is utilized.

FIG. 33 is a sketch of a first embodiment of a valve in accordance withthe invention.

FIG. 33A is an enlarged view of the portion designated 33A in FIG. 33.

FIG. 33B is an alternative actuating device for the embodiment shown inFIG. 33A.

FIG. 34 is a sketch of a second embodiment of a valve in accordance withthe invention.

FIG. 34A is a top view of the embodiment shown in FIG. 34.

FIG. 34B is an enlarged view of the portion designated 34B in FIG. 34A.

FIG. 35 is a sketch of a third embodiment of a valve in accordance withthe invention.

FIG. 35A is an enlarged view of the portion designated 35A in FIG. 35.

FIG. 36 is a sketch of a fourth embodiment of a valve in accordance withthe invention.

FIG. 36A is a partial cross-sectional view of the embodiment shown inFIG. 36.

FIG. 36B is a top view of the embodiment shown in FIG. 36.

FIG. 37 is a sketch of a fifth embodiment of a valve in accordance withthe invention.

FIG. 37A is a partial cross-sectional view of the embodiment shown inFIG. 37.

FIG. 37B is a top view of the embodiment shown in FIG. 37.

FIG. 38 is a sketch of a sixth embodiment of a valve in accordance withthe invention.

FIG. 38A is a partial cross-sectional view of the embodiment shown inFIG. 38.

FIG. 38B is a top view of the embodiment shown in FIG. 38.

FIG. 39 is a sketch of a seventh embodiment of a valve in accordancewith the invention.

FIG. 39A is a partial cross-sectional view of the embodiment shown inFIG. 39.

FIG. 39B is a top view of the embodiment shown in FIG. 39.

FIGS. 40A and 40B are sketches of variations of a valve in accordancewith the invention showing the use of a cylinder valve.

FIGS. 41A and 41B are sketches of variations of a valve in accordancewith the invention showing the use of a cone-shaped valve.

FIG. 42 is an illustration of a discharge valve including stacked driveelements.

FIG. 43 is a “Cussler” model graph indicating the effective aspectratios achieved by compositions of this invention. The graph plotsreduction of permeability vs. volume percentages of filler in barriercoating mixtures of the present invention. Cussler describes severalmodels for the permeability reduction due to oriented layered fillers,which depend on the microstructure expected. For simplicity, thisinvention employs the equation: Pu/P=[1+(a2×2)/(1-X)]/(1-X), where P isthe permeability of the filled material, Pu is the permeability of theunfilled material; a is the aspect ratio of the filler particles; X isthe volume fraction of the filler particles in the coating. Cussler'stheoretical curves for fillers with aspect ratios of 25, 50, 75, and 100are present on the graph. The thick “experimental” data line records theexperimental data points for the barrier coating mixtures. Effectiveaspect ratios can be estimated from the position of the data relative tothe theoretical curves.

FIG. 44 is a graph illustrating the maximum percentage solids and butyllatex (BL100™) to filler ratio vs. percentage by weight of MICROLITE®vermiculite in coating compositions of the invention.

FIG. 45 is a partial cross section of a vehicle passenger compartmentillustrating a curtain airbag in the folded condition prior todeployment.

FIG. 46 is an enlarged view of airbag module shown in FIG. 45.

FIGS. 47A and 47B are cross-sectional views taken along the line 47-47in FIG. 46.

FIG. 48 is a flow chart of a method for designing a side curtain airbagin accordance with the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

1. Airbags

1.1 Plastic Film Airbags

A fundamental problem with the use of plastic films for airbags is thatwhen a single conventional plastic film is used and a tear is(inadvertently) introduced into the film, the tear typically propagateseasily and the airbag fails catastrophically upon deployment. As notedabove, this invention is concerned with various methods of eliminatingthis problem and thus permitting the use of films for airbags with theresulting substantial cost and space savings as well as a significantreduction in injuries to occupants. The reduction in occupant injuryarises from the fact that the film is much lighter than fabric in aconventional airbag and it is the mass of the airbag traveling at a highvelocity which typically injures the out-of-position occupant. Also,since the packaged airbag is considerably smaller than conventionalairbags, the module is also smaller and the total force exerted on theoccupant by the opening of the deployment door is also smaller furtherreducing the injuries to severely out-of-position occupants caused bythe initial stages of the airbag deployment. Finally, in some preferredimplementations of this invention, the airbag is mounted onto theceiling of the vehicle making it very difficult for an occupant to getinto a position as to be injured by the opening of the deployment door.Ceiling mounting of conventional fabric airbags is less practical duetheir excessive size. Ceiling mounting of full protection film airbags,on the other hand, is practical based on the use of the materials and,the reinforcements disclosed here.

One method of solving the tear problem is to use two film airbags or twoairbag layers, one inside the other, where the airbags or layers areattached to each other with an adhesive which is strong enough to holdthe two airbags or layers closely together but not sufficiently strongto permit a tear in one airbag or layer to propagate to the other. If atear is initiated in the outer airbag or layer, for example, and thematerial cannot support significant tensile stresses in the materialclose to the tear, the inner airbag or layer must accommodate theincreased tensile stress until it can be transferred to the outer layerat some distance from the tear. If the tear is caused by a small hole,this increased stress in the inner bag may only occur for a few holediameters away from the hole. If the inner airbag is also made from anelastomer and the outer airbag layer is made from a less elasticmaterial, the outer material can cause the airbag to take on aparticular, desired shape and the inner airbag is used to provide thetear resistance.

In a preferred embodiment, five layers make up the film that is used toconstruct the airbag. The inner layer is a high tensile strength plasticsuch as NYLON® and the two outer layers are elastomeric and also capableof being heat sealed together. The three layers are joined togetherusing an adhesive layer between each adjacent pair of layers resultingin a total of five layers. In addition to blunting the propagation of acrack, the elastomeric layers allow the airbag to be formed by heatsealing the elastic layers together. Additional layers can be added ifparticular properties are desired. Additional layers may also be used atparticular locations where added strength is desired, such as at theseams. Although five layers are described, a preferred embodiment is touse three layers by eliminating one elastic and one adhesive layer.Also, in many cases, the elastic and inelastic layers can be thermallybonded together eliminating the need for the adhesive layer.

The problem which arises with a two airbag system with one airbag insideof and attached to the other, when both film layers have high elasticmoduli and the cause of the tear in one airbag also causes a tear in thesecond airbag, is solved if one of the materials used for the twoairbags has a low modulus of elasticity, such a thermoplastic elastomer.In this case, even though a tear starts in both airbags at the same timeand place, the tear will not propagate in the thermoplastic elastomerand thus it will also be arrested in the high modulus material a shortdistance from the tear initiation point.

An example of a two layer airbag construction is illustrated in FIG. 1which is a perspective view with portions cut away and removed of a filmairbag made from two layers or sheets of plastic film material, whichare preferably substantially coextensive with one another. Frequently, athird adhesive layer is used if the first and second layers cannot bejoined together.

Some of the constructions discussed below contain various materials forreinforcing films. Although not yet available, a promising product forthis purpose is carbon nanotubes. These materials are 100 times strongerthan steel and have one sixth the weight. Such nanotubes have beendemonstrated at Rice University, The University of Texas and TrinityCollege in Dublin, Ireland.

The phenomenon of crack blunting is discussed in some detail in C.-Y.Hui, A. Jagota, S. J. Bennison and J. D. Londono “Crack blunting and thestrength of soft elastic solids”, Proc. R. Soc. London, A(2003) 459,1489-1516. The invention herein makes use of crack blunting to arrestthe propagation of a crack (or tear) by the use of elastic layers on oneor both sides of the more rigid film, typically NYLON®. The NYLON®prevents the stretching of the elastic films and the elastic films serveto both seal the pieces of plastic film to make an airbag and to bluntthe propagation of cracks or tears.

As discussed above and elsewhere herein, the combination of two layersof film wherein one layer comprises a high tensile strength material,such as biaxially oriented Nylon®, and the other generally thicker layercomprises an elastic material, such as polyurethane or a thermoplasticelastomer, not only provides the high strength plus blunting propertybut also permits the stress concentrations in the seams to besubstantially reduced. This is illustrated in FIG. 2 where 590illustrates an airbag including a high tensile strength layer 590 ofNYLON®, for example, 591 an elastic layer of polyurethane, for example,and the joint 592 illustrates the expansion of the elastic layer 591signifying the redistribution of the stresses in the joint 592. Thisstress distribution takes place both along the seam (i.e., into theplane of the drawing) and into the joint 592 (i.e., from right to leftin the drawing). By this process, the maximum stress can be moved fromthe joint 592 to the material away from the joint 592 where the strengthof the high tensile strength material in layer 590 limits the pressurethat the airbag can withstand. By thereby reducing or eliminating thestress concentrations in the joints 592 and/or seams, the thickness andthus the weight of the material making up the airbag is reduced. Thispermits an airbag to be constructed with interconnected compartmentsformed by joining portions of sheet material together, e.g., by heatsealing or vulcanization, to form the desired shape for occupantprotection while minimizing stress concentrations and thus minimizingthe weight of the airbag.

Appendix 1 (of U.S. patent application Ser. No. 10/974,919) provides afinite element analysis for a production side curtain airbag as used onthe AGM Saturn vehicle. The stresses calculated in the seams are shownto require a NYLON® film thickness of about 0.3 mm or about 0.012 inchesto withstand a gage pressure of about 2.8 kg/cm². Through the use of theelastic film techniques described herein, this thickness can bedramatically reduced to about 0.004 inches or lower.

As mentioned above, U.S. Pat. No. 5,811,506 (Slagel) describes athermoplastic, elastomeric polyurethane for use in making vehicularairbags. Slagel does not mention the possibility of this material foruse in a laminated film airbag. The elasticity of this material and thefact that it can be cast or otherwise made into a thin film renders thisan attractive candidate for this application especially due to its hightemperature resistance and other properties. Such a laminated filmairbag would be considerably thinner and have a lighter weight than thepolyurethane material by itself which would have to be quite thick toavoid becoming a balloon.

Another technique which can be used in some situations where particulargeometries are desired is to selectively deposit or laminate metal foilonto particular sections or locations of the airbag. Such a foil notonly greatly reduces gas permeation or leakage through the material butit also adds local stiffness or tensile strength to a particular area ofthe airbag. This can be used, for example, to reinforce the airbag seamsor joints. The most common material for this purpose is aluminum;however, other metals can also be used. Selective addition of metal foilcan also be used to control the shape of the airbag. For someapplications, one layer of the entire airbag can be foil.

Other additives can be used in conjunction with the film airbagsaccording with this invention including, e.g., aluminum trihydrate orantimony trioxide for flame proofing, BPS by Morton Thiokol for mildewprevention and TINUVUN 765 by Ciba Geigy for ozone resistance.

1.2 Driver Side Airbag

In FIG. 1, the driver airbag is shown in the inflated conditiongenerally at 600 with one film layer 601 lying inside a second filmlayer 602. The film layers 601, 602, or sheets of film laminated orotherwise attached together, are non-perforated and are also referred toas airbags or layers herein since they constitute the same. FIG. 1A isan enlarged view of the material of the inner layer 601 and outer layer602 taken within circle 1A of FIG. 1. When manufactured, the film of theinner layer 601 may be made from a thermoplastic elastomer such aspolyurethane, for example, as shown in FIG. 1A, and the outer layer 602may be made from a more rigid material such as NYLON® or polyester. Thetwo film layers 601, 602 are held together along their adjacent regionsby adhesive such as an adhesive 603 applied in a manner sufficient toprovide adherence of the two film layers 601, 602 together, as is knownin the art.

In FIG. 1, a driver side airbag 600 is illustrated where the bag isformed from two flat pieces of material 601, 602 and a centercylindrical piece 604 all of which are joined together using heatsealing with appropriate reinforcement at the heat sealed joints. Heatsealing entails the application of heat to one or both of the surfacesto be joined. In most implementations, the center cylindrical piece 604is not required as taught in U.S. Pat. No. 5,653,464 mentioned above.

The example of FIG. 1 is meant to be illustrative of a general techniqueto minimize the propagation of tears in a composite film airbag. In anactual airbag construction, the process can be repeated several times tocreate a composite airbag composed of several layers, each adjacent pairof layers optionally joined together with adhesive.

The materials used for the various film layers can be the same ordifferent and are generally made from NYLON®, polyethylene or polyester,for the high modulus component and from polyurethane, polyesterelastomer such as HYTREL™ or other thermoplastic elastomers for the lowmodulus component, although other materials could also be used. The useof different materials for the different layers has the advantage thattear propagation and strength properties can complement each other. Forexample, a material which is very strong but tears easily can be used inconjunction with a weaker material which requires a greater elongationbefore the tear propagates or where the tear does not propagate at allas with blunting materials. Alternately, for those cases whereself-shaping is not necessary, all layers can be made from thermoplasticelastomers which expand upon inflation and do not maintain any setshape.

In the implementation of FIG. 1, the adhesive 603 has been applied in auniform coating between the film layers. In some cases, it is preferableto place the adhesive in a pattern so as to permit a tear to propagate asmall distance before the stress is transferred between layers. Thispermits the stress concentration points to move a small distance awayfrom each other in the two films and further reduces the chance that acatastrophic failure will result. Thus, by selecting the pattern of theapplication of the adhesive 603 and/or the location(s) of application ofthe adhesive 603, it is possible to control the propagation of a tear inthe composite airbag 600.

FIG. 1B illustrates an alternate configuration of a composite airbagwhere the outermost airbag 602 has been replaced by a net 605. There maybe additional film layers beneath the inner layer 601 in thisembodiment. A “net” is defined for the purposes of this application asan interlaced or intercrossed network of material, e.g., strips ofmaterial which cross one another. The interlacing may be generated,e.g., by weaving discrete elongate strips of material together or bymolding, casting, progressive coating or a similar process in which casethe material is molded into the network to provide an intercrossedstructure upon formation. Additionally, the net 605 may be formedintegrally with the film material in which case it appears as asubstantial change in material thickness from the net 605 and filmportions of the material to the only film portions of the material. Thestrips of material may be joined at the intersection points in the eventthat discrete material strips are woven together. In the illustratedembodiment, the material strips which constitute the net 605 areoriented in two directions perpendicular to one another. However, it iswithin the scope of the invention to have a net comprising materialstrips oriented in two, non-perpendicular directions (at an angle to oneanother though) or three or more directions so long as the materialstrips are interlaced with each other to form the net. Additionally, thenet pattern can vary from one portion of the airbag to another with theparticular location and orientation determined by analysis to minimizestress concentrations, eliminate wrinkles and folds, or for some otherpurpose. Also, it is understood that the net has openings surrounded bymaterial having a thickness and width substantially smaller than theopenings.

The net 605 may be an integral part of the inner airbag 601 or it can beattached by an adhesive 603, or by another method such as heat sealing,to the inner airbag 601 or it can be left unattached to the inner airbag601 but nevertheless attached to the housing of the airbag system. Inthis case, the stress in the inner airbag 601 is transferred to the net605 which is designed to carry the main stress of the composite airbagand the film of the inner airbag 601 is used mainly to seal and preventthe gas from escaping. Since there is very little stress in the filmlayer constituting the inner airbag 601, a tear will in general notpropagate at all unless there is a failure in the net 605. The net 605in this illustration has a mesh structure with approximately squareopenings of about 0.25 inches. This dimension will vary from design todesign. The adhesive 603 also serves the useful purpose of minimizingthe chance that the net 605 will snag buttons or other objects which maybe worn by an occupant. The design illustrated in FIG. 1B shows the net603 on the outside of the inner airbag 601. Alternately, the net 605 maybe in the inside, internal to the inner airbag 601, especially if it iscreated by variations in thickness of one continuous material.

In one embodiment, the net 605 is attached to the housing of the innerairbag 601 and is designed to enclose a smaller volume than the volumeof the inner airbag 601. In this manner, the inner airbag 601 will berestrained by the net 605 against expansion beyond the volumetriccapacity of the net 605. In this manner, stresses are minimized in thefilm permitting very thin films to be used, and moreover, a film havinga higher elastic modulus can be used. Many other variations arepossible. In one alternative embodiment, for example, the net 605 isplaced between two layers of film so that the outer surface of thecomposite airbag is smooth, i.e., since the film layer is generallysmooth. In another embodiment shown in FIG. 1C, fibers 606 of anelastomer, or other suitable material, are randomly placed and sealedbetween two film layers 601, 602 (possibly in conjunction with theadhesive). In this embodiment, the fibers 606 act to prevent propagationof tears in much the same manner as a net. The net 605 may also beconstructed from fibers.

The driver airbag 600 of FIG. 1 is shown mounted on a vehicle by aconventional mounting structure (not shown) in the driver side positionand inflated in FIG. 1D.

It is understood that the airbag 600 is arranged prior to deployment ina module or more specifically in a housing of the module and furtherthat the interior of the airbag 600 is adapted to be in fluidcommunication with an inflator or inflator system for inflating theairbag, e.g., a gas generation or gas production device. Thus, theinflator is coupled in some manner to the housing. Also, the moduleincludes an initiator or initiation system for initiating the gasgeneration or production device in response to a crash of the vehicle.This structure is for the most part not shown in the drawings but may beincluded in connection with all of the airbag concepts disclosed herein.

An airbag made from plastic film is illustrated in FIG. 3 which is apartial cutaway perspective view of a driver side airbag 610 made fromfilm. This film airbag 610 is constructed from two flat disks or sheetsof film material 611 and 360 which are sealed together by heat weldingor an adhesive to form a seam 613. A hole 617 is provided in one of thesheets 612 for attachment to an inflator (not shown). The hole 617 canbe reinforced with a ring of plastic material 619 and holes 618 areprovided in the ring 619 for attachment to the inflator. A vent hole 615is also provided in the sheet 612 and it can be surrounded by areinforcing plastic disk 616. Since this airbag 610 is formed from flatplastic sheets 611 and 612, an unequal stress distribution occurscausing the customary wrinkles and folds 614.

Several different plastic materials are used to make plastic films forballoons as discussed in U.S. Pat. No. 5,188,558, U.S. Pat. No.5,248,275, U.S. Pat. No. 5,279,873 and U.S. Pat. No. 5,295,892. Thesefilms are sufficiently inelastic that when two flat disks of film arejoined together at their circumferences and then inflated, theyautomatically attain a flat ellipsoidal shape. This is the sameprinciple used herein to make a film airbag, although the particularfilm materials selected are different since the material for an airbaghas the additional requirement that it cannot fail during deploymentwhen punctured.

When the distinction is made herein between an “inelastic” film airbagand an elastic airbag, this difference in properties is manifested inthe ability of the untethered elastic airbag to respond to the pressureforces by becoming approximately spherical with nearly equal thicknessand diameter while the inelastic film airbag retains an approximateellipsoidal shape, or other non-spherical shape in accordance with thedesign of the inelastic film airbag, with a significant differencebetween the thickness and diameter of the airbag.

An analysis of the film airbag shown in FIG. 3 shows that the ratio ofthe thickness to the diameter is approximately 0.6. This ratio can beincreased by using films having greater elasticity. A completely elasticfilm, rubber for example, will form an approximate sphere when inflated.This ratio can also be either increased or decrease by a variety ofgeometric techniques some of which are discussed below. The surprisingfact, however, is that without resorting to complicated tetheringinvolving stitching, stress concentrations, added pieces of reinforcingmaterial, and manufacturing complexity, the airbag made from inelasticfilm automatically provides nearly the desired shape for driver airbagsupon deployment (i.e., the roughly circular shape commonly associatedwith driver side airbags). Note that this airbag still has a less thanoptimum stress distribution which will be addressed below.

Although there are many advantages in making the airbag entirely fromfilm, there is unfortunately reluctance on the part of the automobilemanufacturers to make such a change in airbag design until thereliability of film airbags can be satisfactorily demonstrated. Tobridge this gap, an interim design using a lamination of film and fabricis desirable. Such a design is illustrated in FIG. 4A which is a partialcutaway perspective view of a driver side airbag made from film 622laminated with fabric 621 to produce a hybrid airbag 620. The remainingreference numbers represent similar parts as in the embodiment shown inFIG. 3. In all other aspects, the hybrid airbag 620 acts as a filmairbag. The inelastic nature of the film 622 causes the hybrid airbag620 to form a proper shape for a driver airbag. The fabric 621, on theother hand, presents the appearance of a conventional airbag when viewedfrom the outside. Aside from the lamination process, the fabric 621 maybe attached to the film 622 directly by suitable adhesives, such thatthere are only two material layers, or by heat sealing or any otherconvenient attachment and bonding method. Note, this is not to beconfused with a neoprene or silicone rubber coated conventional driverside airbag where the coating does not significantly modify theproperties of the fabric.

Analysis, as described in the above-referenced U.S. Pat. No. 5,505,485,has shown that a net is much stronger per unit weight than a fabric forresisting tears. This is illustrated in FIG. 4B which is a partialcutaway perspective view of a driver side airbag 610 made from film 612and a net 622, which is preferably laminated to the film 612 or formedfrom the same material as the film 612 and is integral with it, toproduce a hybrid airbag. The analysis of this system is presented in the'485 patent and therefore will not be reproduced here. The referencenumerals designating the element in FIG. 4B correspond to the sameelements as in FIG. 4A.

For axisymmetric airbag designs such as shown in FIGS. 4A-4D, a moreefficient reinforcement geometry is to place the reinforcements in apattern of circular rings 623 and ribs 625 (FIG. 4C). A cross-sectionalview of the material taken along line 4D-4D in FIG. 4C is shown in FIG.4D. In this case, the reinforcement has been made by a progressivecoating process from a thermoplastic elastomeric material such aspolyurethane. In this case, the reinforcing rings and ribs 623, 625 aremany times thicker than the spanning thin film portions 624 and thereinforcing ribs 625 have a variable spacing from complete contact atthe center or polar region to several centimeters at the equator. Thereinforcements may comprise the laminated net as discussed above. Sincethe rings and ribs 623, 625 are formed in connection with the innersurface of the airbag 610, the outer surface of the airbag 610 maintainsits generally smooth surface.

In this regard, it should be stated that plastic manufacturing equipmentexists today which is capable of performing this progressive coatingprocess, i.e., forming a multi-layer plastic sheet (also referred to asa material sheet) from a plurality of different plastic layers. One suchmethod is to provide a mold having the inverse form of the predeterminedpattern and apply the specific plastic materials in individual layersinto the mold, all but the initial layer being applied onto apreexisting layer. The mold has depressions having a depth deeper thanthe remaining portions of the mold which will constitute the thickerregions, the thinner portions of the mold constituting the spanningregions between the thicker regions. Also, it is possible and desirableto apply a larger amount of the thermoplastic elastomer in thedepressions in the mold so that the thicker regions will provide areinforcement effect. In certain situations, it is foreseeable that onlythe thermoplastic elastomer can be coated into the depressions whereas aplastic material which will form an inelastic film layer is coated ontothe spanning regions between the depressions as well as in thedepressions in order to obtain an integral bond to the thermoplasticelastomer. The mold can have the form of the polar symmetric patternshown in FIG. 4C.

The film airbag designs illustrated thus far were constructed from flatplastic sheets which have been sealed by heat welding, adhesive orotherwise. An alternate method to fabricate an airbag is to use amolding process to form an airbag 630 as illustrated in FIG. 5A which isa partial cutaway perspective view of a driver side airbag made fromfilm using blow molding (a known manufacturing process). Blow moldingpermits some thickness variation to be designed into the product, asdoes casting and progressive coating methods molding (other knownmanufacturing processes). In particular, a thicker annular zone 633 isprovided on the circumference of the airbag 630 to give additionalrigidity to the airbag 630 in this area. Additionally, the materialsurrounding the inflator attachment hole 636 has been made thickerremoving the necessity for a separate reinforcement ring of material.Holes 637 are again provided, usually through a secondary operation, forattachment of the airbag 630 to the inflator.

The vent hole 635 is formed by a secondary process and reinforced, or,alternately, provision is made in the inflator for the gases to exhausttherethrough, thereby removing the need for the hole 635 in the bagmaterial itself. Since this design has not been stress optimized, thecustomary wrinkles and folds 634 also appear. The vent hole 635 mightalso be a variable-sized or adjustable vent hole to achieve the benefitsof such as known to those skilled in the art.

One advantage of the use of the blow molding process to manufactureairbags is that the airbag need not be made from flat sheets. Throughcareful analysis, using a finite element program for example, the airbagcan be designed to substantially eliminate the wrinkles and folds seenin the earlier implementations. Such a design is illustrated in FIG. 5Bwhich is a partial cutaway perspective view of a driver side airbag madefrom film using a blow molding process where the airbag design has beenpartially optimized using a finite element airbag model. This design hasa further advantage in that the stresses in the material are now moreuniform permitting the airbag to be manufactured from thinner material.

In some vehicles, and where the decision has been made not to impact thedriver with the airbag (for example if a hybrid airbag is used), theinflated airbag comes too close to the driver if the ratio of thicknessto diameter is 0.6. In these applications, it is necessary to decreasethis ratio to 0.5 or less. For this ratio, thickness means the dimensionof the inflated airbag measured coaxial with the steering column,assuming the airbag is mounted in connection with the steering column,and diameter, or average or effective diameter, is the average diametermeasured in a plane perpendicular to the thickness. This ratio can beobtained without resorting to tethers in the design as illustrated inFIG. 5C which is a side view of a driver side airbag made from filmwhere the ratio of thickness to effective diameter decreases. FIG. 5D isa view of the airbag of FIG. 5C taken along line 5D-5D. This airbag 630can be manufactured from two sheets of material 631 and 632 which arejoined together, e.g., by a sealing substrate, to form seal 633.Inflator attachment hole 636 can be reinforced with a ring of plasticmaterial 360 as described above. Many circumferential geometries can beused to accomplish this reduction in thickness to diameter ratio, oreven to increase this ratio if desired. The case illustrated in FIG. 5Cand FIG. 5D is one preferred example of the use of a finite elementdesign method for an airbag.

Some vehicles have a very steep steering column angle. Direct mountingof an airbag module on the steering wheel will therefore not providegood protection to the driver. One approach to solve this problem can beaccomplished by using a softer wheel rim or column, which adjusts itsangle when pressed by the occupant. However, in some cases this can havejust the opposite effect. If a non-rotating driver side airbag is used,the airbag can be arranged to deploy at a different angle from thesteering wheel without modifying the steering column while the airbagcan be inflated in a direction appropriate for driver protection.Another advantage of using a non-rotating driver side airbag module isthat the angle of the sensor axis is independent of the steering columnangle for self-contained airbag modules.

In a high-speed vehicle crash, the steering column may collapse or shiftdue to the severe crush of the front end of the vehicle. The collapse ofthe steering column can affect the performance of an airbag if the bagis installed on the steering column. One steering system proposed hereinpurposely induces a large stroking of the steering column when thedriver side airbag is activated. This stroking or “disappearing” column,creates a large space in the driver side compartment and thereforeallows the use of a relatively large airbag to achieve betterprotection. In both of the above cases, an airbag module not rotatingwith the steering wheel is the better choice to accomplish occupantprotection.

Recently, there are some developments in steering design, such as“steering by wire”, to eliminate the steering column or the mechanicalmechanism connecting the steering column to the front wheels. Therotation of the steering wheel is converted into a signal which controlsthe turning of front wheels by actuators adjacent to the wheels. Assteer-by-wire is commercialized, it will be advantageous to use theinvention herein of a non-rotating driver side airbag module, which doesnot have to be supported by a steering column.

To provide better viewing to the instrumentation panel for the driver,it is also beneficial to arrange a driver side airbag module so that itdoes not obstruct this view. A non-rotating driver side airbag can beeither arranged to be out of the central portion of the steering wheelor completely out of the steering wheel to avoid this inconvenience.

An inflated airbag 640 interacting with an occupant driver 641 is shownin FIG. 6. Airbag 640 is installed in and deployed from steering wheel642. The steering column 643 has a steep column angle placing the lowerrim 644 of the steering wheel close to the driver 641. When the driver641 moves forward after a crash, the driver's head 645 and the uppertorso 646 make contact with the airbag 640 and the steering wheel 642.The airbag 640 is then deformed and pushed by the occupant 641 so thatthe airbag 640 does not form a cushion between the upper torso 646 andthe steering wheel 642 even though the occupant's driver's head 645 isin full contact with the airbag 640.

A modified column 648 is illustrated in FIG. 7, which is equipped with ajoint 647 between a lower part 648A of the steering column 648 connectedto the vehicle and an upper part 648B of the steering column 648connected to the steering wheel 642. Joint 647 allows the steering wheel642 and the inflated airbag 640 to have a variable angle relative to thelower part 648A of the steering wheel 648 and thus an adjustable angleto the driver 641. Appropriate rotation of the joint 647 enables theinflated airbag 640 to align with the head 645 and upper torso 646 ofthe driver 641. The protection offered by the steering column 648including the airbag 640 system in FIG. 7 is an improvement over thesystem in FIG. 6 since the airbag 640 is in a better orientation tocushion the occupant driver 641 and penetration of the lower rim 644 ofthe steering wheel 642 is avoided. The concept of a self-aligned driverside airbag can also be accomplished by rotating the steering wheel 642or utilizing a soft rim for the steering wheel 642.

Construction of the joint 647 may involve use of a pivot hinge havingtwo parts pivotable relative to one another with one part being attachedto the lower part 648A of the steering column 648 and the other partbeing attached to the upper part 648B of the steering column 648.Alternatively, one of the lower and upper parts 648A, 648B can be formedwith a projecting member and the other part formed with a fork-shapedmember and a pivot pin connects the projecting member and fork-shapedmember. Other ways to construct joint 647 will be apparent to thoseskilled in the art in view of the disclosure herein and are encompassedby the description of joint 647.

Pivotal movement of the upper part 648B of the steering column 648 andthus the steering wheel 642 and airbag 640 mounted in connectiontherewith may be realized manually by the driver or automatically by anactuating mechanism. The actuating mechanism can be designed tocooperate with an occupant position and monitoring system to receive thedetected position and/or morphology of the driver 641 and then adjustthe steering wheel 642 to a position within a range of optimum positionsfor a driver in that position and/or with that morphology. To allow forsituations in which the driver manually changes the position of thesteering wheel 642 outside of the range, the actuating mechanism can bedesigned to cooperate with a crash sensor system to receive a signalindicative of an impending or actual crash and then automatically adjustthe position of the upper part 648B of the steering column 648. In thismanner, even if the driver has the steering wheel 642 set in a positionduring regular driving in which it will adversely affect airbagdeployment, the actuating mechanism causes the steering wheel 642 to bere-positioned during the crash

A design with an airbag and an inflator on the steering column isillustrated in FIG. 8. The steering column can comprise an outer shaft651, an inner shaft 652, and a supporting bracket 653. Outer shaft 651can be coupled with the steering wheel 654 at one end region andextended to the engine compartment at the other end region to drive thesteering mechanism 655 which causes turning of the tire(s) of thevehicle. The inner shaft 652 can be coupled with the inflator and airbagmodule 656 at one end region while the other end region can be attachedto a stationary part 657 of the vehicle chassis in the enginecompartment, for example. The supporting bracket 653 can be fixed to thefirewall 658 for support. Bearings 659 and 660 can be placed between thebracket 653 and the outer shaft 651 to rotatably support the outer shaft651 on the bracket 653 and bearings 661 and 662 can be placed betweenthe outer shaft 651 and the inner shaft 652 and can be used forrotatably supporting the outer shaft 651 on the inner shaft 652. Theouter and inner shafts 651, 652 may be tubular and concentric to oneanother.

Inner shaft 652 is stationary, not rotating with the steering wheel 654,therefore the airbag in airbag module 656 can be designed in anarbitrary shape and orientation. For example, a large airbag can bedesigned to provide the optimal protection of the driver. A less rigidsteering wheel or column can also reduce the force exerted on the driverand allow the airbag to align with the driver. For example, the curvedportion 663 of the steering wheel 654 can be designed to be flexible orto move away when the force on the rim of the steering wheel 654 exceedsa certain level. This force can be measured by appropriate measurementdevices or sensors and a processor used to determine when the curvedportion 663 of the steering wheel 654 should be moved away.

Steering wheel 654 can have a central cavity in which the inflator andairbag module 656 is situated. This central cavity may be centered abouta rotation axis of the steering wheel 654.

Although module 656 is referred to as an inflator and airbag module, itis conceivable that only the airbag is arranged in the steering wheel654, i.e., in the cavity defined thereby, while the inflator portion isarranged at another location and the inflation gas is directed into theairbag, e.g., the inflator is arranged on the dashboard and inflatinggas directed into the airbag via a passage in the inner shaft 652.

A driver side restraint system, which is installed on or in thedashboard 675 of a vehicle is depicted in FIG. 9. The inflated airbag671 fills the space between the ceiling of the passenger compartment672, the windshield 673, the steering wheel 674, the dashboard 675, andthe occupant driver 676. The airbag 671 is of such a geometry that theoccupant driver 676 is surrounded by air cushion after the airbag 671 isfully inflated. An additional improvement can be provided if thesteering wheel 674 and column strokes and sinks toward the dashboard 675increasing the space between the occupant driver 676 and the steeringwheel 674. The stroking movement of the steering wheel 674 and columncan be initiated by the restraint system crash sensor. One approach isto use a mechanism where pins 678 lock the column and the steering wheel674. As soon as the sensor triggers to initiate the airbag 671, the pinscan be released and the steering wheel 674 and the column can then movetowards the firewall 677. Other mechanisms for enabling movement of thesteering wheel 674, i.e., the steering column to sink toward thedashboard 675, can be used in the invention.

An airbag 680 installed on the dashboard 681 of a vehicle is illustratedin FIG. 10. The airbag 680 is partially deployed between the windshield682 and the steering wheel 683 and the dashboard 681. The inflator 685provides gas to unfold and inflate the airbag 680. A torsional spring686, or other mechanism, can be used to control the opening of a valve687, which controls the flow of gas out of vent hole 688 of the airbag680. When the pressure inside the airbag 680 is lower than a desiredpressure, the valve 687 can close retaining the gas within the airbag680. When the pressure inside the airbag 680 exceeds a design level, thevalve 687 opens and releases gas from the airbag 680 into the enginecompartment 689, which is separated from the passenger compartment byfirewall 690. Although only a single vent hole 688 and associated valve687 are shown, multiple vent holes and/or valves can be provided.

A distributed inflator and airbag module 691 along the dashboard of avehicle below the windshield 692 is illustrated in FIG. 11A. FIG. 11Billustrates a side view of the inflator and airbag module 691, whichshows the module cover 693, the folded airbag 694, the inflator 695 andthe vent hole 696 covering an opening in the airbag 694. The longtubular inflator 695, which has multiple ports along the module 691, canevenly and quickly generate gas to inflate the airbag 694. Multiple ventholes 696 are shown in FIG. 11A, located near the bottom of thewindshield 692. These vent holes 696, since they cover openings in theairbag 694, can direct, or allow the flow of, the exhaust gases from theairbag 694 into the engine compartment. More specifically, vent holes696 can be used regulate the gas flow from the airbag 694 to the enginecompartment so that the inflated airbag 694 can be matched to theoccupant and the severity of the crash.

Airbag 694 may be attached to the dashboard so that the periphery of theopening in the airbag 694 associated with each vent hole 696 is alignedwith the vent hole 696.

Drive-by-wire is being considered for automobiles. Such a system willpermit a significant reduction in the mass and cost of the steeringwheel and steering column assembly. However, if the airbag is stilldeployed from the steering wheel, the strength and thus weight of theairbag will have to be largely maintained. Thus, a preferablearrangement is to cause the steering wheel and column to move out of theway and have the airbag for the driver deploy from the dashboard or theceiling as discussed elsewhere herein. Such an airbag can bemulti-chambered so as to better capture and hold the driver occupant inposition during the crash.

1.3 Passenger Side Airbag

The discussion above has been limited for the most part to the driverside airbag which is attached to the vehicle steering wheel or otherwisearranged in connection therewith. This technology is also applicable toa passenger side airbag, which is generally attached to the instrumentpanel, as illustrated in FIG. 12 which is a partial cutaway perspectiveview of a passenger side airbag 700 made from three pieces or sheets offlat film 701, 702 and 703 which have joined seams 704 between adjacentpieces of film 701, 702, 703. The passenger side airbag, as well as rearseat airbags and side impact airbags, generally have a different shapethan the driver side airbag but the same inventive aspects describedabove with respect to the driver side airbag could also be used inconnection with passenger side airbags, rear seat airbags and sideimpact airbags. Although illustrated as being constructed from aplurality of sheets of plastic film, the passenger side airbag 700 canalso be made by blow molding or other similar molding process, i.e., asone unitary sheet. Also, for many vehicles, the film sheet 702 isunnecessary and will not be used thereby permitting the airbag to onceagain be manufactured from only two flat sheets. The inflator attachmenthole 706 is now typically rectangular in shape and can be reinforced bya rectangular reinforcement plastic ring 708 having inflator-mountingholes 707. A vent hole 705 can also be provided to vent gases from thedeploying airbag 700. The vent hole 705 might be a variable-sized oradjustable vent hole to achieve the benefits of such as known to thoseskilled in the art.

Another class of airbags that should be mentioned are side impactairbags that deploy from the vehicle seat or door. These also can bemade from plastic film according to the teachings of this invention.

1.4 Inflatable Knee Bolster-Knee Airbag

An example of a knee airbag is illustrated in FIG. 13 which is aperspective view of a knee restraint airbag illustrating the support ofthe driver's knees and also for a sleeping occupant lying on thepassenger seat of the vehicle (not shown). The knee support airbag showngenerally at 514 comprises a film airbag 515 which is composed ofseveral smaller airbags 516, 517, 518, and 519 as disclosed above.Alternately, the knee airbag can be made from a single film airbag asdisclosed in U.S. Pat. No. 5,653,464 referenced above. The knee supportairbag can be much larger than airbags previously used for this purposeand, as a result, offers some protection for an occupant, not shown, whois lying asleep on the vehicle seat prior to the accident.

With the development of the film airbag and the inflator design above, avery thin airbag module becomes possible as disclosed in U.S. Pat. No.5,505,485. Such a module can be made in any length permitting it to beused at many locations within the vehicle. For example, one could bepositioned on the ceiling to protect rear seat occupants. Another onewould stretch the length of the car on each side to protect both frontand rear occupants from head injuries in side impacts. A module of thisdesign lends itself for use as a deployable knee restraint as shown inFIG. 13. Eventually, especially when drive-by-wire systems areimplemented and the steering wheel and column are redesigned oreliminated, such an airbag system will be mounted on the ceiling andused for the protection of all of the front seat passengers and driverin frontal impacts. With the economies described above, airbags of thistype will be very inexpensive, perhaps one-fifth the cost of currentairbag modules offering similar protection.

In FIG. 13, a knee protection airbag for the front driver is showngenerally at 709 (and is also referred to as a knee bolster herein).Since the knee airbag 709 fills the entire space between the knees andthe instrument panel and since the instrument panel is now located at asubstantial distance from the occupant's knees, there is substantiallymore deflection or stroke provided for absorbing the energy of theoccupant. Submarining is still prevented by inflating the knee airbag709 to a higher pressure, typically in excess of 1 bar and sometimes inexcess of 2 bars, and applying the force to the occupant knees before heor she has moved significantly. Since the distance of deployment of theknee airbag 709 can be designed large enough to be limited only by theinteraction with an occupant or some other object, the knee airbag 709can be designed so that it will inflate until it fills the void belowthe upper airbag, not illustrated in this figure. The knee protectionairbag 709 can take the form of a fabric or any of the composite airbagsdisclosed above, e.g., include a plastic film layer and an overlyingnet, or two or more plastic film layers, usually at least one isinelastic to provide the shape of the knee bolster and at least one iselastic to control the propagation of a tear. The knee bolster airbagcan also be deployed using as aspirated inflator or other methodpermitting the airbag to be self-limiting or self-adjusting so as tofill the space between the knees of the occupant and the vehiclestructure. In FIG. 13, the width of the cells is typically less than thewidth of the knee of an occupant. In this manner, the capturing of theknees of the occupant to prevent them from sliding off of the kneeairbag 709 is enhanced.

In preferred designs presented herein and below, the knee airbag 709 isdeployed as a cellular airbag with the cells, frequently in the form oftubes, interconnected during inflation and, in most cases, individualvalves in each chamber close to limit the flow of gas out of the chamberduring the accident. In this manner, the occupant is held in positionand prevented from submarining. A composite film is one preferredmaterial, however, fabric can also be used with some increased injuryrisk. The cellular or tubular airbags designs described herein are alsosometimes referred as compartmentalized airbags.

Normally, the knee bolster airbag will not have vents. It will bedeployed to its design pressure and remain deployed for the duration ofthe accident. For some applications, a vent hole will be used to limitthe peak force on the knees of the occupant. As an alternate toproviding a fixed vent hole as illustrated in the previous examples, avariable vent hole can be provided as shown in FIGS. 30 and 30A(discussed below). Alternately, this variable vent function can beincorporated within the inflator as described in U.S. Pat. No.5,772,238.

Typically, inflatable knee bolster installations comprise an inflatableairbag sandwiched between a rigid or semi-rigid load distributing impactsurface and a reaction surface. When the inflator is triggered, theairbag expands to move the impact surface a predetermined distance to anactive position. This position may be determined by tethers between thereaction and impact surfaces. These installations comprise numerousparts, bits and pieces and require careful installation. In contrast, ina preferred knee bolster described herein, there is no rigid loaddistributing surface but rather, the knee bolster conforms to the shapeof the knees of the occupant. Tethers in general are not required orused as the shaping properties of inelastic films are utilized toachieve the desired airbag shape. Finally, preferred designs herein arenot composed of numerous parts and in general do not require carefulinstallation. One significant problem with the use of load distributionplates as is commonly done in the art is that no provision is made tocapture the knees and thus, especially if the crash is an angular impactor if the occupant is sitting on an angle with respect to the kneebolster or has his or her legs crossed, there is a tendency for theknees to slip sideways off of the knee bolster defeating the purpose ofthe system. In the multi-cellular knee bolster disclosed herein, thecells expand until they envelop the occupant's knees, capturing them andpreventing them from moving sideways. Once each cell is filled to adesign pressure, a one-way valve closes and flow out of the cell isprevented for the duration of the crash. This design is especiallyeffective when used with an anticipatory sensor as the knees can becaptured prior to occupant movement relative to the passengercompartment caused by the crash. A signal from the anticipatory sensorwould initiate an inflator to inflate the knee bolster prior to orsimultaneous with the crash.

An improvement to this design, not illustrated, is to surround theairbags with a net or other envelope that can slide on the surface ofthe airbag cells until they are completely inflated. Then, when theoccupant begins loading the airbag cells during the crash, displacementof the knees not only compresses the cells that are directly in linewith the knees but also the adjacent cells thus providing a significantincrease to the available effective piston area to support the knees inmuch the same way that a load distribution plate functions. Such a netor envelope effectively distributes the load over a number of cells thuslimiting the required initial pressure within the airbag cells. Othermethods of accomplishing this load distribution include the addition ofsomewhat flexible stiffeners into the surface of the airbag where itcontacts the knees, again with the goal of causing a load on one cell tobe partially transferred to the adjacent cells.

In a preferred design, as discussed below, the cellular airbags inflateso as to engulf the occupant by substantially filling up all of thespace between the occupant and the walls of the passenger compartmentfreezing the occupant in his or her pre-crash position and preventingthe occupant from ever obtaining a significant velocity relative to thepassenger compartment. This will limit the acceleration on the occupantto below about 15-20 Gs for a severe 30 MPH barrier crash. This retainsthe femur loads well below the requirements of FMVSS-208 and canessentially eliminate all significant injury to the occupant in such acrash. This, of course, assumes that the vehicle passenger compartmentis effectively designed to minimize intrusion, for example.

In most of the preferred designs disclosed herein, the surface thatimpacts the occupant is a soft plastic film and inflicts little if anyinjury upon impact with the occupant. Even the fabric versions when usedas a knee bolster, for example, can be considered a soft surfacecompared with the load distribution plates or members that impact theknees of the occupant in conventional inflatable knee bolster designs.This soft impact is further enhanced when an anticipatory sensor is usedand the airbags are deployed prior to the accident as the deploymentvelocity can be substantially reduced.

In a conventional airbag module, when the inflator is initiated, gaspressure begins to rise in the airbag which begins to press on thedeployment door. When sufficient force is present, the door breaks openalong certain well-defined weakened seams permitting the airbag toemerge from its compartment. The pressure in the airbag when the dooropens, about 10 to 20 psi, is appropriate for propelling the airbagoutward toward the occupant, the velocity of which is limited by themass of the airbag. In the case of a film airbag, this mass issubstantially less, perhaps by as much as a factor of three or more,causing it to deploy at a much higher velocity if subjected to thesehigh pressures. This will place unnecessary stresses in the material andthe rapid movement of the airbag past the deployment door could induceabrasion and tearing of the film by the deployment door. A film airbag,therefore, must be initially deployed at a substantially lower pressure.However, conventional deployment doors require a higher pressure toopen. This problem is discussed in detail in the above-referencedpatents and patent applications where, in one implementation, apyrotechnic system is used to cut open the door according to theteachings of Barnes et al. (U.S. Pat. No. 5,390,950).

There are of course many ways of making inflatable knee restraints usingchambered airbags, such as illustrated in U.S. Pat. No. 6,685,217,without deviating from the teachings of this invention.

1.5 Ceiling Deployed Airbags

Airbags disclosed herein and in the assignee's prior patents arebelieved to be the first examples of multi-chambered airbags that aredeployed from the ceiling and the first examples of the use of tubularor cellular airbags. These designs should become more widely used asprotection is sought for other situations such as preventing occupantsfrom impacting with each other and when developments in drive-by-wireare implemented. In the former case, airbags will be interposed betweenseating positions and in the latter case, steering wheel assemblies willbecome weaker and unable to support the loads imposed by airbags. Insome cases, in additional to support from the ceiling, these airbagswill sometimes be attached to other surfaces in the vehicle such as theA, B and C pillars in much the way that some curtain airbags now receivesuch support.

One method of forming a film airbag is illustrated generally at 710 inFIG. 14. In this implementation, the airbag is formed from two flatsheets or layers of film material 711, 712 which have been sealed, e.g.,by heat or adhesive, at joints 714 to form long tubular shapedmini-airbags 713 (also referred to herein as compartments or cells) inmuch the same way that an air mattress is formed. In FIG. 14, a singlelayer of mini-airbags 713 is shown. It should be understood that themini-airbags 713 are interconnected to one another to allow theinflating gas to pass through all of the interior volume of the airbag710. Also, the joints 714 are formed by joining together selected,opposed parts of the sheets of film material 711, 712 along parallellines whereby the mini-airbags 713 are thus substantially straight andadjacent one another. In other implementations, two or more layers couldbe used. Also, although a tubular pattern has been illustrated, otherpatterns are also possible such as concentric circles, waffle-shaped orone made from rectangles, or one made from a combination of thesegeometries or others. The film airbag 710 may be used as either a sideairbag extending substantially along the entire side of the vehicle, anairbag disposed down the center of the vehicle between the right andleft seating positions or as a rear seat airbag extending from one sideof the vehicle to the other behind the front seat (see FIG. 15) and mayor may not include any of the venting arrangements described herein.

FIG. 15 is a perspective view with portions removed of a vehicle havingseveral deployed film airbags. Specifically, a single film airbag havingseveral interconnected sections, not shown, spans the left side of thevehicle and is deployed downward before being filled so that it fitsbetween the front seat and the vehicle side upon inflation (an airbagspanning the right side of the vehicle can of course be provided). Thisprovides substantial support for the airbag and helps prevent theoccupant from being ejected from the vehicle even when the side windowglass has broken. A system which also purports to prevent ejection isdescribed in Bark (U.S. Pat. No. 5,322,322 and U.S. Pat. No. 5,480,181).The Bark system uses a small diameter tubular airbag stretchingdiagonally across the door window. Such a device lacks the energyabsorbing advantages of a vented airbag however vents are usually notdesired for rollover protecting airbags. In fact, the device can act asa spring and can cause the head of the occupant to rebound and actuallyexperience a higher velocity change than that of the vehicle. This cancause severe neck injury in high velocity crashes. The airbag of Bark'322 also is designed to protect primarily the head of the occupant,offering little protection for the other body parts. In contrast to thecompletely sealed airbag of Bark, a film airbag of the present inventioncan have energy absorbing vents and thus dampens the motion of theoccupant's head and other body parts upon impact with the film airbag.Note that the desirability of vents typically goes away whenanticipatory sensors are used as discussed elsewhere herein.

The airbag of Bark '322 covers the entire vehicle opening and receivessupport from the vehicle structure, e.g., it extends from one side ofthe B-pillar to the other so that the B-pillar supports the airbag 720.In contrast to the tube of Bark, the support for a preferred embodimentof the invention disclosed herein in some cases may not requirecomplicated mounting apparatus going around the vehicle door and downthe A-pillar but is only mounted to or in the ceiling above the sidedoor(s). Also, by giving support to the entire body and adjusting thepressure between the body parts, the airbag of the present inventionminimizes the force on the neck of the occupant and thus minimizes neckinjuries.

3.5.1 Side Curtain Airbags

In FIG. 15, a single side protection airbag for the driver side isillustrated at 720. A single front airbag spans the front seat forprotection in frontal impacts and is illustrated at 723 with the ceilingmounted inflator at 724. A single airbag is also used for protection ofeach of the rear seat occupants in frontal impacts and is illustrated at725. With respect to the positioning of the side airbag 720, the airbag720 is contained within a housing 722 which can be position entirelyabove the window of the side doors, i.e., no portion of it extends downthe A-pillar or the B-pillar of the vehicle (as in Bark '322). The sideairbag housing 722 thus includes a mounting structure (not shown) formounting it above the window to the ceiling of the vehicle and such thatit extends across both side doors (when present in a four-door vehicle)and thus protects the occupants sitting on that side of the vehicle fromimpacting against the windows in the side doors. To ensure adequateprotection for the occupants from side impacts, as well as frontalimpacts and roll-overs which would result in sideward movement of theoccupants against the side doors, the airbag housing 722 is constructedso that the airbag 720 is initially projected in a downward directionfrom the ceiling prior to inflation and extends at least substantiallyalong the entire side of the ceiling. This initial projection may bedesigned as a property of the module 722 which houses the airbag 720,e.g., by appropriate construction and design of the module and itscomponents such as the dimensioning the module's deployment door anddeployment mechanism.

Although a variety of airbag designs can be used as the side impactprotection airbag, one preferred implementation is when the airbagincludes first and second attached non-perforated sheets of film and atear propagation arresting mechanism arranged in connection with each ofthe film sheets for arresting the propagation of a tear therein. A netmay also be used as described above. The net would constrict or tensionthe airbag if it were to be designed to retain an interior volume lessthan the volume of the airbag (as discussed above).

The airbag can include a venting device (e.g., a venting aperture asshown in FIGS. 4A and 4B) arranged in connection with the airbag forventing the airbag after inflation thereof. In certain embodiments, theairbag is arranged to extend at least along a front portion of theceiling such that the airbag upon inflation is interposed between apassenger in the front seat of the vehicle and the dashboard (thisaspect being discussed below with respect to FIG. 19).

FIG. 16 is a view looking toward the rear of the vehicle of the deployedside protection airbag of FIG. 15. An airbag vent is illustrated as afixed opening 721. Other venting designs are possible including ventingthrough the airbag inflator as disclosed in the above-referenced patentsand patent applications as well as the variable vent described belowwith reference to FIGS. 30 and 30A or even no vent for rolloverprotection.

The upper edge of the airbag is connected to an inflator 722 and thatthe airbag 720 covers the height of the window in the door in thisimplementation.

FIG. 16A is a view of a side airbag similar to the one of FIG. 16although with a different preferred shape, with the airbag 720 removedfrom the vehicle. The parallel compartments or cells can be seen. Thisaspect is discussed below with reference to FIGS. 24-26.

3.5.2 Frontal Curtain Airbags

FIGS. 17 and 18-18D illustrate the teachings of this invention appliedin a manner similar to the airbag system of Ohm in U.S. Pat. No.5,322,326. The airbag of Ohm is a small limited protection systemdesigned for the aftermarket. It uses a small compressed gas inflatorand an unvented thin airbag which prevents the occupant from contactingwith the steering wheel but acts as a spring causing the occupants headto rebound from the airbag with a high velocity. The system of FIG. 17improves the performance of and greatly simplifies the Ohm design byincorporating the sensor and compressed gas inflator into the samemounting assembly which contains the airbag. The system is illustratedgenerally at 730 in FIG. 17 where the mounting of the system in thevehicle is similar to that of Ohm.

In FIG. 18, the module assembly is illustrated from a view lookingtoward the rear of the airbag module of FIG. 17 with the vehicleremoved, taken at 18-18 of FIG. 17. The module 730 incorporates amounting plate 731, a high pressure small diameter tube constituting aninflator 733 and containing endcaps 734 which are illustrated here ashaving a partial spherical surface but may also be made from flatcircular plates. The mounting plate 731 is attached to the vehicle usingscrews, not illustrated, through mounting holes 735. An arming pin 729is illustrated and is used as described below.

FIG. 18A is a cross sectional view of the airbag module of FIG. 18 takenat 18A-18A and illustrates the inflator initiation system of thisinvention. The inflator 733 is illustrated as a cylindrical tube,although other cross sectional shapes can be used, which contains a hole730 therein into which is welded by weld 732 to an initiation assembly737. This assembly 737 has a rupture disk 738 welded into one end. Arupture pin 739 is positioned adjacent rupture disk 738 which will bepropelled to impact the rupture disk 738 in the event of an accident asdescribed below. When disk 738 is impacted by pin 739, it fails therebyopening essentially all of the orifice covered by disk 738 permittingthe high pressure gas which is in a tube of the inflator 733 to flow outof the tube 733 into cavity 740 of initiator assembly 737 and thenthrough holes 741 into cavity 742. Cavity 742 is sealed by the airbag736 which now deploys due to the pressure from the gas in cavity 742.

When the vehicle experiences a crash of sufficient severity to requiredeployment of the airbag 736, sensing mass 743, shown in phantom, beginsmoving to the left in the drawing toward the front of the vehicle.Sensing mass 743 is attached to shaft 744 which in turn is attached toD-shaft 745 (see FIG. 18C). As mass 743 moves toward the front of thevehicle, D-shaft 745 is caused to rotate. Firing pin 747 is held andprevented from moving by edge 746 of D-shaft 745. However, when D-shaft745 rotates sufficiently, edge 746 rotates out of the path of firing pin747 which is then propelled by spring 748 causing the firing pin pointto impact with primer 749 causing primer 749 to produce high pressuregas which propels pin 739 to impact disk 738 releasing the gas frominflator tube 733 inflating the airbag 736 as described above. Thesensor 743,744, D-shaft 745 and primer mechanism 747, 748, 749 aresimilar to mechanisms described in U.S. Pat. No. 5,842,716.

FIG. 18B is a cross sectional view, with portions cutaway and removed,of the airbag module 730 of FIG. 18 taken at 18B-18B and illustrates thearming pin 729 which is removed after the module 730 is mounted onto thevehicle. If the module 730 were to be dropped accidentally without thisarming pin 729, the sensor could interpret the acceleration from animpact with the floor, for example, as if it were a crash and deploy theairbag 736. The arming system prevents this from happening by preventingthe sensing mass 743 from rotating until the arming pin 729 is removed.

FIG. 19 is a perspective view of another preferred embodiment of theairbag of this invention 720 shown mounted in a manner to provideprotection for a front and a rear seat occupant in side impactcollisions and to provide protection against impacts to the roof supportpillars in angular frontal impacts and to offer some additionalprotection against ejection of the occupant.

More particularly, in this embodiment, an airbag system for protectingat least the front-seated occupant comprises a single integral airbag720 having a frontal portion 726 sized and shaped for deploying in frontof the front-seated occupant and a side portion 727 sized and shaped fordeploying to the side of the front-seated occupant. In this manner,airbag 720 wraps around the front-seated occupant during deployment forcontinuous front to side coverage. An inflator (not shown) is providedfor inflating the single integral airbag with gas. As shown, the sideportion 727 may be sized and shaped to deploy along an entire side ofthe vehicle, the side portion 727 is longer than the frontal portion 726and the frontal portion 726 and side portion 727 are generally orientedat a 90 degree angle relative to each other. As with the other sidecurtain airbags discussed in connection with FIGS. 15, 16, 16A and 19,the airbag 720 may be housed in the ceiling. Also, as noted throughoutthis application, airbag 720 may comprise one or more sheets of film andthe tear propagation arresting structure or a net may be provided totension or constrict the deployment of the airbag 720. The constructioncan also comprise straight or curved interconnected cells or tubularstructures.

FIGS. 20 and 21 illustrate another embodiment of the invention intendedto provide protection from side impacts and rollover accidents not onlyfor a person in the front seat of a motor vehicle such as a motor car,but also for a person in the rear seat of the vehicle which is similarto that shown in FIGS. 15, 16 and 16A.

Referring to FIG. 20, the housing 715 is provided over both the frontdoor 716 and the rear door 750. The airbag or other type of inflatableelement 751 is shown in the inflated state in FIG. 21. The inflatableelement 751 has its top edge 752 secured to a part of the housing 715 orceiling of the passenger compartment that extends above the doors 716,750 of the motor vehicle (see, e.g., FIG. 16A). The design of theinflatable element is similar to that shown in FIG. 14 or 16A, with theinflatable element including a plurality of parallel cells orcompartments 752, which when inflated are substantially cylindrical. Agas generator 750 is provided which is connected to the inflatableelement 751 in such a way that when the gas generator 750 is activatedby a sensor 751 to supply gas to the cells 752. Sensor 751 may beseparate as shown or formed integrally with the gas generator 750, orwhich is otherwise associated with the gas generator 750, and respondsto a crash condition requiring deployment of the inflatable element 751to activate the gas generator 750. Thus, as the inflatable element 751inflates, the cells 752 inflate in a downward direction until theinflatable element 751 extends across the windows in the doors 716, 750of the motor vehicle (see FIG. 16). As the inflatable element 751inflates, the length of the lower edge thereof decreases by as much as30% as a consequence of the inflation of the cells 752. This reductionin the length of the lower edge ensures that the inflated element 751 isretained in position as illustrated in FIG. 21 after it has beeninflated. Although shown as parallel tubes, other geometries are ofcourse possible such as illustrated in FIGS. 28A-28L.

The inflatable element 751 described above incorporates a plurality ofparallel substantially vertical, substantially cylindrical cells 752.The inflatable element 751 may be made of interwoven sections of amaterial such as film or other material such as woven fabric. Such ainterweaving of material comprises a first layer that defines the frontof the inflatable element 751, i.e., the part that is visible in FIGS.20 and 21, and a second layer that defines the back part, i.e., the partthat is adjacent the window in FIGS. 20 and 21, whereby selected partsof the first region and the second region are interwoven to define linksin the form of lines where the front part and the back part of theinflatable element are secured together. A technique for making aninflatable element of inter-woven sections of material is described inInternational Patent Publication No. WO 90/09295.

The tubes or cells 752 can be further joined together as illustrated inFIG. 22A by any method such as through the use of an additional sheet ofmaterial 753 which joins the front and back edges 754 and 755 of theadjacent cells 752 in order to render the inflatable element 751 moreresistant to impacts from parts of the body of an occupant. Theadditional chambers 756 formed between the additional sheet of material753 and the front and back edges of the cells 752 can either bepressurized at the same pressure as the tubes or cells 752 or they canbe left exposed to the atmosphere, as is preferred. Although illustratedas joining adjacent cells of the inflatable element 751, they canalternatively be arranged to join non-adjacent cells. Although the cellsare illustrated as parallel tubes, any geometry of chambers, cells ortubes can benefit from this improvement including those as illustratedin FIGS. 28A-28L.

FIG. 22 is a cross section showing the nature of the cells 752 of theinflatable element 751 of FIGS. 20 and 21. It can be seen that the cells752 are immediately adjacent to each other and are only separated bynarrow regions where the section of material, e.g., film, forming thefront part of the inflatable element 751 has been woven or otherwiseattached by heat sealing or adhesive with the section of materialforming the back part of the inflated element.

Also, as noted throughout this application, inflatable element 751 mayhave any of the disclosed airbag constructions. For example, inflatableelement 751 may comprise one or more sheets of film and the tearpropagation arresting mechanism or a net may be provided to tension orconstrict the deployment of the inflatable element 751. The film surfacefacing the occupant need not be the same as the film facing the sidewindow, for example. In order to prevent broken glass, for example, fromcutting the airbag, a thicker film, a lamination of a film and a fabricor a film and a net can be used.

There are of course many ways of making ceiling-mounted frontalprotection airbags using chambers without departing from the teachingsof this invention such as disclosed in published patent applicationsWO03093069, 20030234523 and 20030218319. Such airbags can be made fromtubular sections or sections of other shapes and the amount ofdeployment of such airbags can be determined by occupant sensors asdisclosed in other patents assigned to the assignee of this patent. Suchairbags can be flat as disclosed herein or other shapes.

3.5.3 Other Compartmentalized Airbags

As mentioned above, anticipatory crash sensors based on patternrecognition technology are disclosed in several of assignee's patentsand pending patent applications. The technology now exists based onresearch by the assignee to permit the identification and relativevelocity determination to be made for virtually any airbag-requiredaccident prior to the accident occurring. This achievement now allowsairbags to be reliably deployed prior to the accident. The implicationsof this are significant. Prior to this achievement, the airbag systemhad to wait until an accident started before a determination could bemade whether to deploy one or more of the airbags. The result is thatthe occupants, especially if unbelted, would frequently achieve asignificant velocity relative to the vehicle passenger compartmentbefore the airbags began to interact with the occupant and reduce his orher relative velocity. This would frequently subject the occupant tohigh accelerations, in some cases in excess of 40 Gs, and in many casesresulted in serious injury or death to the occupant especially if he orshe is unrestrained by a seatbelt or airbag. On the other hand, avehicle typically undergoes less than a maximum of 20 Gs during even themost severe crashes. Most occupants can withstand 20 Gs with little orno injury. Thus, as taught herein, if the accident severity could beforecast prior to impact and the vehicle filled with plastic filmairbags that freeze the occupants in their pre-crash positions, thenmany lives will be saved and many injuries will be avoided.

One scenario is to use a camera, or radar-based or terahertz-basedanticipatory sensor to estimate velocity and profile of impactingobject. From the profile or image, an identification of the class ofimpacting object can be made and a determination made of where theobject will likely strike the vehicle. Knowing the stiffness of theengagement part of the vehicle allows a calculation of the mass of theimpacting object based on an assumption of the stiffness impactingobject. Since the impacting velocity is known and the acceleration ofthe vehicle can be determined, we know the impacting mass and thereforewe know the severity or ultimate velocity change of the accident. Fromthis, the average chest acceleration that can be used to just bring theoccupant to the velocity of the passenger compartment during the crashcan be calculated and therefore the parameters of the airbag system canbe set to provide that optimum chest acceleration. By putting anaccelerometer on the airbag surface that contacts the occupant, theactual chest acceleration can be measured and the vent size can beadjusted to maintain the calculated optimum value. With this system,neither crush zone or occupant sensors are required, thus simplifyingand reducing the cost of the system and providing optimum results evenwithout initiating the airbag prior to the start of the crash.

There is of course a concern that if the airbags are inflated too early,the driver may lose control of the vehicle and the accident would bemore severe than in the absence of such early inflation. To put thisinto perspective, experiments and calculations show that a reasonablemaximum time period to inflate enough airbags to entirely fill a normalsedan is less than 200 ms. To protect the occupants of such a vehicle byfilling the vehicle with airbags before the accident would requireinitiating deployment of the airbags about 200 ms prior to the accidentwhich corresponds to a distance of vehicle travel of approximately 15feet for the case where two vehicles are approaching each other with aclosing velocity of about 60 MPH. It is unlikely that any action takenby the driver during that period would change the outcome of theaccident and when the sensor signals that the airbags should bedeployed, a control system can take control of the vehicle and preventany unstable motions.

FIG. 23 illustrates one preferred method of substantially filling thepassenger compartment with airbags. Primary airbag 760 along withsecondary airbags 761, 762, and 763 prior to inflation are attached toone or more aspirated inflators 776 and stored, for example, within theheadliner or ceiling of the vehicle. When the anticipatory or othercrash sensor, not shown, determines that deployment is necessary,primary airbag 760 deploys first and then secondary airbags 761-763deploy from gas that flows through airbag 760 and through one-way valves764. Inflation continues until pressure builds inside the airbags760-763 indicating that they have substantially filled the availablevolume. This pressure buildup reduces and eventually stops theaspiration and the remainder of the gas from the gas generator flowseither into the airbags 760-763 to increase their pressure or into thepassenger compartment. Since the pumping ratio of the aspiratedinflators 776 is typically above 4, approximately 75% of the gas in theairbags 760-763 comes from the passenger compartment thus minimizing thepressure increase in the passenger compartment and injuries to the earsof the occupants. This also permits the substantial filling of thepassenger compartment without the risk of breaking windows or poppingdoors open. If additional pressure relief is required then it can beachieved, for example, by practicing the teachings of U.S. Pat. No.6,179,326.

In a similar manner, primary airbag 765 inflates filling secondaryairbags 766-770 through one-way valves 771. Additionally, airbags 775mounted above the heads of occupants along with secondary airbags 772can be inflated using associated inflators 776 to protect the heads ofthe occupants from impact with the vehicle roof or headliner. Ifoccupant sensors are present in the vehicle, then when the rear seat(s)is (are) unoccupied, deployment of the rear-seat located airbags can besuppressed.

The knees and lower extremities of the occupants can be protected byknee airbags 780 and secondary airbags 779 in a similar manner. Thedesign of these airbags will depend on whether there is a steering wheel774 present and the design of the steering wheel 774. In some cases, forexample, a primarily airbag may deploy from the steering wheel 774 whilein other cases, when drive-by-wire is implemented, a mechanism may bepresent to move the steering wheel 774 out of the way permitting thesecondary airbag(s) 779 to be deployed in conjunction with the kneeairbag 780. The knee airbag deployment will be discussed in more detailbelow.

FIG. 23A illustrates a view from the top of the vehicle with the roofremoved taken along line 23A-23A in FIG. 23 with the vehicle unoccupied.As can be seen, primary airbag 760, for example, is actually a row oftubular structures similar to that shown in FIG. 14. Additionally,curtain airbags 786 are present only in this implementation and theyalso comprise several rows of tubes designed to contact the occupantsand hold them away from contacting the sides of the vehicle. Airbags 787are also advantageously provided down the center of the vehicle tofurther restrain the occupants and prevent adjacent occupants fromimpacting each other.

In the preferred design, support for the airbags relies of substantiallyfilling the vehicle and therefore loads are transferred to the walls ofthe vehicle passenger compartment. In many cases, this ideal cannot becompletely achieved and straps of tethers will be required to maintainthe airbags in their preferred locations. Again, this will depend of thedesign and implementation of this invention to a particular vehicle.

The particular designs of FIGS. 23 and 23A are for illustrative purposesonly and the particular method of substantially filling a portion of thepassenger compartment with airbags will depend substantially on thevehicle design.

An alternate design is illustrated in FIG. 24 where a cellular airbag790 deploys from the steering wheel in a somewhat conventional mannerand additional lateral tubes 791 deploy between the occupant and thewindshield. These airbags also provide added support for the steeringwheel airbag for those cases where drive-by-wire has been implementedand the heavy structural steering wheel and column has been replaced bya lighter structure.

FIG. 25 illustrates an example wherein cellular tubular airbags madefrom thin plastic film, for example, expand is a flower pattern toengage the occupants and receive support from the walls, ceiling etc. ofthe passenger compartment. The airbags deform and interact with eachother and the occupants to conform to the available space and to freezethe occupants in their pre-crash positions. Airbags 792 come from theceiling for upper body protection. Airbags 793 deploy from the upperinstrument panel for upper body protection and airbags 794 deploy forlower body protection. Airbags 795 protect the knees and lowerextremities and airbags 796 protect the rear seated occupants. Finally,airbags 797 again provide protection for the tops of the heads of theoccupants. Although not shown in this drawing, additional airbags may beprovided to prevent the lateral movement of the occupants such ascurtain and center-mounted airbags. Again, the intent is to fill as muchof the vehicle passenger compartment surrounding the occupant aspossible. If occupant sensors are present and the absence of arear-seated occupant, for example, can be detected, then the rear seatairbags need not be deployed.

FIGS. 26 and 26A illustrate an example of a flower-type airbag design.The inflator 800, preferably an aspirated inflator, discharges into acommon distribution volume or manifold, which can be made from theplastic film, which distributes the gas to the cells or tubes 802 of theairbag assembly through one-way valves 804, formed in the sheet of thetubes 802, in a manner similar to the tubular airbags of FIG. 23. Anenvelope 803 of plastic film is provided to contain the tubes 802.Alternately, the tubes 802 can be connected together along theiradjacent edges and the envelope 803 eliminated.

FIGS. 27 and 27A illustrate an example of a knee bolster airbag 805 andits inflation sequence. Only four tubes are illustrated althoughfrequently, a larger number will be used. The inflation gas comes fromthe inflator, not shown, into a manifold 807 which distributes the gasinto the tubes 806 through one-way valves 808 formed in the material ofthe airbag 805. During inflation, the airbag 805 unrolls in a mannersimilar to a Chinese whistle.

In some of the implementations illustrated here, the airbags do not havevent holes. At the end of the crash, the gas in the airbags should beallowed to exhaust, which generally will occur through the inflatorhousing. Vents in the airbags for the purpose of dissipating the kineticenergy of the occupants can, in many cases, be eliminated since thephilosophy is to freeze the occupant before he or she has achievedsignificant velocity relative to the passenger compartment. In otherwords, there will be no “second collision”, the term used to describethe injury producing impact of the occupant with the walls of thepassenger compartment. The occupants will, in general, experience thesame average deceleration as the vehicle which in a 30 mph barrier crashis significantly less than 20 Gs.

FIGS. 28A, 28D, 28F, 28H, 28J and 28L illustrate six related prior artcurtain airbag designs that have been modified according to teachings ofthis invention to include the use of an envelope or a material sheetthat spans the cells or tubes that make up the curtain airbag. Thecurtain airbag of FIG. 28A, designated 810, is a design based onparallel vertical tubes 811 and can be made from fabric or plastic film.Sheets of fabric or film material 812 are attached to the outer edges oftubes 81 so as to span from one tube to the adjacent tubes asillustrates in FIG. 28B which is a view of FIG. 28A taken along line28B-28B. The volumes created between the tubes 811, i.e., cells, can bepressurized as illustrated in FIG. 28C or left exposed to the atmosphereas illustrated in FIG. 28B. The particular geometry that the cells willacquire is shown simplified here. In reality, the cell geometry willdepend on the relative lengths of the various material sections, thethickness of the material and the relative inflation pressures of eachcell. Care must be exercised in the design to assure that resultingairbag will fold properly into the storage area. The presence of theenvelope of spanning sheets renders the curtain airbag 810 significantlymore resistant to deformation on impact from the head of the occupant,for example. This improves the ability of the airbag to retain theoccupant's head within the vehicle during a side impact or rollover. Themain function of the curtain airbag 810 is to prevent this partialejection which is the major cause of injury and death in side impact androllover accidents. Although the envelope or spanning sheets 812 addadditional material to the airbag 810, the added stiffness createdactually permits the use of thinner materials for the entire airbag 810and thus reduces the total weight and hence the cost of the airbag 810.

FIGS. 28D and 28E illustrate an alternate geometry of a side curtainairbag where the tubes acquire a varying thickness and shape. Curtainairbag 813 has tubes 814 and an envelope or spanning sheet 815. FIGS.28F and 28G illustrate still another geometry of a side curtain airbagwhere the tubes 817 are formed by joining islands between the opposingsheets of material. As in all of the cases of FIGS. 28A, 28D, 28F, 28H,28J and 28L, various manufacturing processes can be used to join theopposing sheets of material including sewing, heat sealing, adhesivesealing and interweaving where the entire bag is made in one passthrough the loom, among others. Curtain airbag 816 has tubes 817 and anenvelope or spanning sheet 818 (FIGS. 28F and 28G).

FIGS. 28H and 28I illustrate another geometry of a side curtain airbagwhere the tubes again acquire a roughly rectangular shape. Curtainairbag 819 has tubes 820 and an envelope or spanning sheet 821. FIGS.28J and 28K illustrate yet another alternate geometry of a side curtainairbag where the tubes are slanted but still retain a roughlyrectangular shape. Curtain airbag 822 has tubes 823 and an envelope orspanning sheet 824.

Finally, FIGS. 28L and 28M illustrate still another geometry of a sidecurtain airbag where the tubes again acquire a roughly rectangular shapewith the tubes running roughly fore and aft in the vehicle. Curtainairbag 825 has tubes 826 and an envelope or spanning sheet 827.

Deployment of an airbag from the vehicle trim such as the headliner,A-Pillar, B-Pillar, C-Pillar was believed to be first disclosed in thecurrent assignee's patents referenced above. As airbags begin to fillmore and more of the passenger compartment as taught here and in otherpatents to the current assignee, the edges of the passenger compartmentor the locations where the walls of the passenger compartment joinbecome attractive locations for the deployment of airbags. This isespecially the case when the airbags are made from thin plastic filmthat can be stored at such locations since they occupy a minimum ofspace. Thus, storage locations such as disclosed in U.S. PatentApplication Publication No. 20030178821 are contemplated by this andprevious inventions by the current assignee. For some applications, itis possible to put the entire airbag system in the headliner if kneeprotection is not required. This is a problem for convertible vehicleswhere the edges of the passenger compartment become more important.

The size of the cells or tubes in the various airbag designs discussedabove can vary according to the needs of the particular application. Fora given internal pressure, the thickness of the film material decreasesas the diameter of the tubes decreases. Since the thickness determinesthe weight of the airbag and thus the potential to cause injury onimpact with an occupant, in general, an airbag made from multiplesmaller tubes will cause less injury than a single-chambered airbag ofthe same size. Therefore, when possible the designs should use moresmaller cells or tubes. In the extreme, the vehicle can be filled with alarge number of small airbags each measuring three inches or less indiameter, for example, and as long as the passenger compartment issubstantially filled at least between the occupant and the compartmentin the direction of the crash, the exact positioning of a particularairbag becomes less important as each one will receive support fromothers and eventually the passenger compartment walls.

Through the implementation of the ideas expressed herein, the airbagsystem becomes truly friendly. It can deploy prior to the accident,freeze the occupant in his or her pre-crash position, impact theoccupant without causing injury, and gradually deflate after theaccident. Inflators would preferably be aspirated to draw most of therequired gas from the passenger compartment. Since an aspirated inflatorautomatically adjusts to provide just the right amount of gas, onlysingle stage pyrotechnic systems would be required. Occupant sensorswould not be necessary as the system would adjust to all occupantsregardless of whether they were seated in a rear-facing child seat,belted, unbelted, out-of-position, lying down, sleeping, had their feetin the dashboard, etc. By eliminating the dual stage inflator, usingaspiration thereby greatly reduces the amount of propellant required andby using thin plastic film, this airbag system is not only by far thebest performing system it is also potentially the least expensivesystem.

In FIG. 29, the advantages of the self-limiting airbag system disclosedherein and in U.S. Pat. No. 5,772,238 and with reference to FIG. 15,when used with a rear-facing child seat, are illustrated. In this case,where multiple film airbags are illustrated, the airbags deploy but thedeployment process stops when each of the film airbags interacts withthe child seat and the pressure within each bag rises to where the flowis stopped. In this case, the child 666 is surrounded by airbags 664 andfurther protected from the accident rather than being injured as is thecase with current design airbags. The airbags 664 can be additionallysurrounded by a net or other envelope 665 most of which has been cutawayand removed in the figure. In other implementations, a single airbagwill be used in place of the multiple airbags illustrated here ormultiple attached airbags can be used eliminating the need for the net.

The self-limiting feature is illustrated here by either a variableorifice exhaust port in the airbag, discussed in more detail below, or,preferably, provision is made in the airbag inflator itself asillustrated in the referenced '238 patent where a close-down of theaspiration system is used during the deployment portion of the processand a smaller variable orifice is used during the deflation portion. Theaspiration cutoff can be designed so that the airbag deploys until thepressure begins to rise within the bag which then stops the inflationprocess, closes the aspiration ports and the airbag then becomes stifferto absorb the kinetic energy of the impacting occupant. Thus, during thedeployment phase, very little force is exerted on the occupant, or thechild seat, but as the occupant begins to move into and load the airbag,substantial force is provided to limit his or her motion.

1.6 Rear of Seat Mounted Airbags

FIG. 25, discussed above, illustrates airbags that deploy from the rearof the front seat to protect rear seat occupants of a vehicle in acrash. These airbags also provide protection for front seat occupants tohelp prevent unbelted occupants in the rear seat from moving into thefront seat during a crash and causing injury to those occupants seatedin the front seat.

1.7 Exterior Airbags

Airbags that deploy outside of the vehicle have been disclosed primarilyfor side impact in the current assignee's patents. Generally, theseexternally deployed airbags are based on the use of an anticipatorysensor that identifies that an accident is about to occur using, forexample, pattern recognition technologies such as neural network.Normally, these airbags are made from fabric but as the properties offilms improve, these fabric airbags will be replaced by film airbags. Inparticular, using technology available today, the combination of a filmand a reinforcing net can now be used to construct externally deployedairbags that are both stronger and lighter in weight than fabric. U.S.Patent Publication No. 20030159875 discloses the use of a resin for apedestrian protection airbag. All of the film airbag constructionsillustrated herein for interior use are also applicable for external usewith appropriate changes in dimensions, material properties etc. asneeded to satisfy the requirements of a particular application.

Particular mention should be made of pedestrian protection since this israpidly becoming a critical safety issue primarily in Japan and Europewhere the percentage of people killed in automobile accidents that arepedestrians is greater than in North America. Although many patents havenow issued and are pending relating to pedestrian airbags, none, exceptthose of the current assignee, are believed to make use of ananticipatory sensor that can identify that the vehicle is about toimpact with a pedestrian. See, e.g., U.S. Patent Publication No.20030159875 and EP01338483A2. Since this technology has been developedby the current assignee, the technology is now available to identifythat a pedestrian is about to be struck by the vehicle. This technologyuses a camera or other imaging system and a pattern recognition systemsuch as a neural network or combination network as defined in theabove-referenced current assignee's patents.

Exterior airbags can require a substantial amount of gas for inflationand thus are candidates for aspirated inflators such as disclosed inU.S. Patent Application Publication No. 20020101067 and above herein.Exterior airbags can get quite large and thus require a substantialamount of gas. Also they frequently require a high pressure. Aspiratedinflators can economically satisfy both of these requirements. Suchexterior airbags can also be of the shape and construction as disclosedherein and illustrated, for example, in U.S. Patent ApplicationPublication No. 20040011581. Such exterior airbags can be made fromplastic film.

1.8 Variable Vent

A great deal of effort has gone into the design on “smart” inflatorsthat can vary the amount of gas in the airbag to try to adjust for theseverity of the crash. The most common solution is the dual stage airbagwhere either of two charges or both can be initiated and the timingbetween the initiation can be controlled depending on the crash.Typically, one charge is set off for low speed crashes and two forhigher speed crashes. The problem, of course, is to determine theseverity of the crash and this is typically done by a passengercompartment-mounted crash sensor. This is relatively easy to do forbarrier crashes but the crashes in the real world are quite different.For example, some pole crashes can appear to be mild at the beginningand suddenly become severe as the penetrating pole strikes the engine.In this case, there may not be time to initiate the second charge. Analternate solution, as reported in current assignee's patents listedabove, is to use a single stage inflator but to control the flow of gasinto and/or out of the airbag. If this is an aspirated inflator, thiscontrol happens automatically and if the airbag is a film airbag, it canbe designed to interact with any occupant and thus inflator control isnot required.

In an alternate situation where either a conventional inflator is usedor an aspirated inflator is used, the flow out of the airbag can bemanaged to control the acceleration of the chest of the occupant. Mostairbags have a fixed vent hole. As an alternate to providing a fixedvent hole as illustrated in the previous examples, a variable vent holecan be provided as shown in FIGS. 30 and 30A, where FIG. 30 is a partialcutaway perspective view of a driver side airbag made from film having avariable vent in the seam of the airbag. In this embodiment of anairbag, a hinged elastic member or flap 835 is biased so that it tendsto maintain vent 830 in a closed position. As pressure rises within theairbag, the vent 830 is forced open as shown in FIG. 30 and FIG. 30A,which is a detail of the vent 830 shown in FIG. 30 taken along line30A-30A of FIG. 30. This construction enables the use of a smallerinflator and also reduces the maximum chest acceleration of the occupantin a crash and more accurately controls the deceleration of theoccupant. In FIGS. 30 and 30A, vent 830 contains an opening 833 formedbetween film layer 834 and reinforcement member 832. Film layer 831 isalso sealed to reinforcing member 832. Member 835 is attached toreinforcing member 832 (via portion 837) through film 834. A weakenedsection 836 is formed in member 835 to act as a hinge. The elasticity ofthe material, which may be either metal or fiber reinforced plastic orother suitable material, is used to provide the biasing force tending tohold the variable opening closed. The variable vent can also beaccomplished through controlling the flow back through the inflatorassembly. This latter method is particularly useful when aspiratedinflators and self limiting airbags are used. For other variable ventdesigns, see the discussion about FIGS. 33-42.

FIG. 31 shows a typical chest G pulse experienced by an occupant and theresulting occupant motion when impacting an airbag during a 35-MPHfrontal impact in a small vehicle. When the variable orifice airbag isused in place of the conventional airbag, the chest acceleration curveis limited and takes the shape similar to a simulation result shown inFIG. 32. Since it is the magnitude of the chest acceleration thatinjures the occupant, the injury potential of the airbag in FIG. 32 issubstantially less than that of FIG. 31.

Since the variable exhaust orifice remains closed as long as thepressure in the airbag remains below the set value, the inflator needonly produce sufficient gas to fill the airbag once. This isapproximately half of a gas which is currently produced by standardinflators. Thus, the use of a variable orifice significantly reduces thetotal gas requirement and therefore the size, cost and weight of theinflator. Similarly, since the total amount of gas produced by allinflators in the vehicle is cut approximately in half, the total amountof contaminants and irritants is similarly reduced or alternately eachinflator used with the variable orifice airbag is now permitted to besomewhat dirtier than current inflators without exceeding the totalquantity of contaminants in the environment. This in turn, permits theinflator to be operated with less filtering, thus reducing the size andcost of the inflator. The pressure buildup in the vehicle is alsosubstantially reduced protecting the occupants from ear injuries andpermitting more or larger airbags to be deployed.

Characteristics of inflators vary significantly with temperature. Thus,the mass flow rate of gas into the airbag similarly is a significantfunction of the temperature of the inflator. In conventional fixedorifice airbags, the gas begins flowing out of the airbag as soon aspositive pressure is achieved. Thus, the average pressure in the airbagsimilarly varies significantly with temperature. The use of a variableorifice system as taught by this invention however permits the bags tobe inflated to the same pressure regardless of the temperature of theinflator. Thus, the airbag system will perform essentially the samewhether operated at cold or hot temperature, removing one of the mostsignificant variables in airbag performance. The airbag of thisinvention provides a system which will function essentially the same atboth cold and hot temperatures.

The variable orifice airbag similarly solves the dual impact problemwhere the first impact is sufficient to trigger the crash sensors in amarginal crash where the occupant is wearing a seatbelt and does notinteract with the airbag. A short time later in a subsequent, moreserious accident, the airbag will still be available to protect theoccupant. In conventional airbags using a fixed orifice, the gasgenerator may have stopped producing gas and the airbag may have becomedeflated.

Since the total area available for exhausting gas from the airbag can besubstantially larger in the variable orifice airbag, a certain amount ofprotection for the out-of-position occupant is achieved even when theaspiration system of the referenced '238 patent is not used. If theoccupant is close to the airbag when it deploys, the pressure will beginto build rapidly in the airbag. Since there is insufficient time for thegas to be exhausted through the fixed orifices, this high pressureresults in high accelerations on the occupant's chest and can causeinjury. In the variable orifice embodiment, however, the pressure willreach a certain maximum in the airbag and then the valve would open toexhaust the gas as fast as the gas generator is pumping gas into theairbag thus maintaining a constant and lower pressure than in the formercase. The airbag must be sufficiently deployed for the valve to beuncovered so that it can operate. Alternately, the valving system can beplaced in the inflator and caused to open even before the cover opensthereby handling the case where the occupant is already against thedeployment door when the airbag deployment is initiated.

Many geometries can be used to achieve a variable orifice in an airbag.These include very crude systems such as slits placed in the bag inplace of round exhaust vents, rubber patches containing one or moreholes which are sewn into the bag such that the hole diameter getslarger as the rubber stretches in response to pressure in the bag, plusa whole variety of flapper valves similar to that disclosed herein. Slitsystems, however, have not worked well in experiments and rubber patchesare affected by temperature and thus are suitable only for very crudesystems. Similarly, the bag itself could be made from a knittedmaterial, which has the property that its porosity is a function of thepressure in the bag. Thus, once again, the total amount of gas flowingthrough the bag becomes a function of the pressure in the bag.

Although the case where the pressure is essentially maintained constantin the bag through the opening of a valve has been illustrated, it ispossible that for some applications, a different function of thepressure in the bag may be desirable. Thus, a combination of a fixedorifice and variable valve might be desirable. The purpose of adjustingthe opening area of an airbag vent hole is to control the gas flow rateout of the vent hole according to the pressure inside the airbag. If thepressure is higher, then the area of the vent hole becomes larger andallows more gas to flow out. By regulating the pressure inside anairbag, the force applied on an occupant is minimized.

A superior solution to the problem is to place an acceleration sensor onthe surface to the airbag that contacts the chest of the occupant, or isexpected to contact the chest of the occupant or the forwardmost part ofthe occupant. An electronic controlled valve can then be coupled to theaccelerometer and the acceleration of the chest of the occupant can becontrolled to limit this acceleration below some value such as 40 Gs.Alternately, if the severity of the crash has been accurately forecast,then the airbag can provide the minimum deceleration to the occupant'schest to bring the occupant to the same speed as the vehicle passengercompartment at the time the airbag has become deflated.

When airbags are used in conjunction with an anticipatory sensor toinflate and hold occupants in their pre-crash position, they usuallywill not have vents for dissipating the kinetic energy of the occupantssince the occupants will never attain a significant velocity relative tothe vehicle. Usually, it will be desirable to retain such airbags intheir inflated state for several seconds and then to deflate them topermit the occupants to egress from the vehicle. There are severalmethods of permitting such airbags to deflate including: opening theaspiration vent when aspirated inflators are used; electrically and/ormechanically opening the airbags when the pressure drops belowatmospheric pressure; chemically, thermally melting or burning orotherwise opening a hole in such an airbag after a predetermined timeperiod or perhaps two seconds (for example) after the vehicle motion hasstopped; etc.

1.8.1 Discharge Valves for Airbags

FIG. 33 shows an airbag 841 equipped with a discharge valve 842 inaccordance with a first embodiment of the invention. The discharge valve842 is interposed between the gas-filled interior of the airbag and anatmosphere exterior of the airbag 841 so as to enable gas or other fluidfrom the airbag to the outlet from the interior of the airbag to theexterior atmosphere. Discharge valve 842 is situated separate and apartfrom an opening in the airbag 841 through which gas flows into theinterior of the airbag 841.

The airbag 841 may be any airbag arranged on or in a vehicle, includingbut not limited to, a frontal airbag, a side airbag, a knee bolster andan externally deployed airbag.

As shown in FIG. 33A, discharge valve 842 comprises a fixed, bottomplate 843 arranged in connection with or associated with the airbag 841,e.g., on an outer layer of the material of the airbag or arranged inconjunction with the inflator, and has a pattern of openings. Bottomplate 843 may overlie one or more openings in the airbag 841. A topplate 844 is arranged over the bottom plate 843 and is movable relativeto the bottom plate 843. Top plate 844 has the same pattern of openingsas the bottom plate 843. Top plate 844 is mounted to a fix component inthe vehicle by a spring 845 to allow for movement relative to the bottomplate 843 to thereby vary the correspondence between the openings in thetop plate 844 and the bottom plate 843.

When the phrase “pattern of openings” is used to refer to thearrangement of openings in the bottom plate 843 and top plate 844, itmust be understood that the openings are not required to be arranged inany discernible or specific geometric pattern. Rather, the pattern maysimply be the overall arrangement of the openings.

Gas from the airbag 841 flows through the openings in the bottom plate843 and then through the openings in the top plate 844 with the volumeand/or flow rate of the gas being determined by the degree ofcorrespondence between the openings in the top plate 843 and theopenings in the bottom plate 843. That is, in a maximum gas outflowposition, the top plate 844 will be in a position so that openings inthe top plate 844 correspond exactly with the openings in the bottomplate 843. On the other hand, in a minimum gas outflow position, the topplate 843 will be in a position so that the openings in the top plate843 will over lie solid portions of the bottom plate 843. Any positionbetween these extreme positions is also possible so that the gas outflowrate is controlled by the variable position of the top plate 843relative to the bottom plate 843.

A movement mechanism is provided to move the top plate 843 relative tothe bottom plate 843 and is generally effective to move the top plate843 to multiple positions relative to the bottom plate 843 and forvariable, adjustable durations. That is, the top plate 843 can be movedfrom one position to another position during the discharge of gas fromthe airbag 841 to vary the outflow of gas during the discharge. Movementof the top plate 843 and timing of the movement of the top plate 843 maybe controlled by an appropriate control system to obtain the desiredoutflow rate, duration and/or volume of gas from the airbag 841. Thecontrol system can be designed to consider the properties of theoccupant to be protected by the airbag 841, e.g., the occupant'sposition, morphology, type and identification.

One embodiment of the movement mechanism comprises a piezo-electricbi-morph crystal arrangement 18 which shakes the top plate 843 back andforth (in the direction of arrow A) to thereby modulate the valveopenings defined by the openings in the bottom plate 843 and top plate843. The piezo-electric crystal 846 is driven by a drive signal andassociated electronics 847. The electronics 847 can be connected to orincorporated into a vehicle occupant sensor capable of determining anoptimum discharge rate of the airbag 841 so that the top plate 843 ismoved to achieve the optimum discharge rate.

Another movement mechanism could be an inductive actuator or motorarrangement with a cam offset (represented by motor 847A in FIG. 33B).In this case, the motion could be started during a pre-crash period andengaged with a magnetic clutch or piezo-electric clutch thereafter. Amotor can also be used which is offset by the pitch of the openings andthereby achieve the possibility of regulating the valve openings definedby the openings in the top plate 843 and fixed plate 843.

Referring now to FIG. 34, another embodiment of a discharge valve isshown designated generally as 848. In this embodiment, an indent orgroove 849 is formed in a metal foil diaphragm 850 in a peripheralsurface of the airbag 841 (see FIG. 34A), or in a surface against whichthe pressure in the airbag 841 is effective. A signal is fed to acircuit formed by the groove 849 so that there is a large impedance(I²R) drop across the groove that melts the metal foil and therebyweakens the diaphragm 850. The pressure of the gas in the airbag 841will then cause the weakened region to break and open a passage betweenthe interior of the airbag 841 and the exterior. A 12 V firing signalmay be preferably used.

Several grooves can be provided on the metal foil diaphragm 850 toenable different size openings to be formed. Instead of metal foil, thediaphragm may be made of any material which melts upon the formation ofan electric circuit. The grooves 849 can be annular and concentric.

When multiple annular grooves or rings 849 are provided, with anassociated circuit formed for each groove 849, a signal can be sent to aparticular circuit to cause an opening having a pre-determined size tobe formed, i.e., the weakened region will be at a set diameter from acenter of the diaphragm 850. In this manner, a logic input can be usedto determine what size opening is needed to provide for a controlled,appropriate discharge and then generate a signal to cause the annulargroove 849 which will provide for that size opening to weaken andsubsequently break upon exertion of the pressure from the gas in theairbag 841.

Referring now to FIGS. 35 and 35A, another embodiment of a dischargevalve is shown. In this embodiment, the discharge valve 851 comprises anelastomer diaphragm 852 with apertures 853 therein. In a rest condition,the diaphragm 852 is flat and the apertures 853 are relatively small.However, when pressure is applied, the diaphragm 852 expands to thecondition shown in FIG. 35 and the apertures 853 become larger. Gas fromthe interior of the airbag 841 flows to the exterior through theenlarged apertures 853. The expansion of the diaphragm 852 depends onthe magnitude of the pressure of the gas in the airbag 841.

The edges of the diaphragm 852 are preferably fixed relative to theairbag 841 and may even be attached to the airbag 841. For example, theedges of the diaphragm 852 may be attached to the outer material layerof the airbag 841.

Control of the flow rate and/or volume of gas from the airbag 841 can beachieved through appropriate determination of the size and/or number ofthe apertures 853.

The material from which the diaphragm 852 is made is preferablypre-stretched and then die cut. Instead of an elastomer, other resilientand/or flexible materials may be used.

Referring now to FIGS. 36, 36A and 36B, in this embodiment, a dischargevalve for an airbag is represented generally as 854. The discharge valveincludes a fixed aperture disk 855 arranged in connection with orassociated with the airbag 841 and a movable aperture disk 856 mountedover the fixed disk 855. Fixed disk 855 may overlie one or more openingsin the airbag 841. Movable disk 856 has alternating solid sections 857and open sections 858 and is connected to an arm 859. The center of disk856 is mounted through the fixed disk 855 by a mounting pin 860,although this mounting arrangement can be eliminated and other devicesfor mounting the movable disk 856 relative to the fixed disk 855employed in the invention. Arm 859 is associated with a rotationmechanism 861 to enable the arm 859 to be moved in the directions ofarrow B. Movement of the arm 859 results in movement of the movable disk856 relative to the fixed disk 855 so that the correspondence betweenthe apertures in the fixed disk 855 and the apertures in the movabledisk 856 is varied (to thereby adjust valve openings defined by theapertures in the fixed disk 855 and movable disk 856). This variationenables the discharge flow to be controlled.

The rotation mechanism 861 may be a solenoid, bi-morph piezo-electricelement, ferromagnetic arrangement or drive, ferroelectric arrangementor drive or a thermal-based arrangement, e.g., a phase change metal.That is, almost any type of controllable mechanism for moving the arm859 can be used in the invention. When a solenoid is used, applicationof alternating electrical current causes forward and reverse motions ofthe arm 859.

FIGS. 37, 37A and 37B show another embodiment of a discharge valve inaccordance with the invention and is designated generally as 862.Discharge valve 862 includes a valve seat 863 formed in connection withor associated with the airbag 841 and arranged to enable flow of gasfrom the interior of the airbag 841 therethrough. Valve seat 863 mayoverlie one or more openings in the airbag 841. A valve member 864engages with the valve 863 and a valve spring 865 is arranged to providea biasing force to press the valve member 864 toward the airbag 841 toclose the opening(s) formed by the valve seat 863 and valve member 864.

FIGS. 38, 38A and 38B show another embodiment of a discharge valve foran airbag in accordance with the invention and is designated generallyas 866. Discharge valve 866 includes a substrate 867 having three ormore spiral cuts 868 arranged to form cantilevered arms 869 that willdeflect under pressure. The cantilevered arms 869 may be die cut intothe material of the airbag 841. Multiple spiral arms thus form aplurality of springs. In operation, the pressure of the gas in theinterior of the airbag 841 will urge the arms 869 upward as shown inFIG. 38 thereby opening the cuts to form passages at the locations ofthe cuts 868.

Instead of die cutting the cantilevered arms 869 into the material ofthe airbag 841, a dedicated diaphragm may be provided in connection withan outer material layer of the airbag 841 and cuts made in thisdiaphragm.

FIGS. 39, 39A and 39B show another embodiment of a discharge valve foran airbag in accordance with the invention and is designated generallyas 870. Discharge valve 870 includes a substrate 871 cut in a specificmanner to define a square cantilevered spring matrix having a centralregion 872 and cantilevered arms 873 that will deflect under pressure.The cantilevered arms 873 may be die cut into the material of the airbag841. Multiple spiral arms thus form a large spring valve. In operation,the pressure of the gas in the interior of the airbag 841 will urge thearms 86 upward as shown in FIG. 39 thereby raising the central region872 and opening passages between the interior of the airbag 841 and theexterior.

Instead of die cutting the cantilevered arms 873 into the material ofthe airbag 841, a dedicated diaphragm may be provided in connection withan outer material layer of the airbag 841 and cuts made in thisdiaphragm.

Referring now to FIGS. 40A and 40B, instead of plates having a patternof openings interposed between the airbag interior and airbag exterior,a pair of cylinders could be used.

As shown in FIGS. 40A and 40B, an inner cylinder 874 has a pattern ofopenings and is positionable inside an outer cylinder 875 such that thepattern of openings in the outer cylinder 875 are in alignment with thepattern of openings in the inner cylinder 874. Outer cylinder 875 iscoupled to a motor 876 or other actuating device for moving the outercylinder 875 in a stroked manner in the direction of arrow A, in whichcase, the outer cylinder 875 is moved up and down relative to the innercylinder 874 (FIG. 40A). The pattern of openings in the inner cylinder874 may completely align with the pattern of openings in the outercylinder 875 when the outer cylinder 875 is fully in the up position.

The motor 876 is controlled by a gas discharge rate determination unit880, e.g., a processor containing an algorithm relating the desired gasdischarge rate to the required action of the motor 876 to move the outercylinder 875 to provide for the desired gas discharge rate. Such analgorithm may be determined experimentally or empirically. The gas ratedetermination unit 880 is provided with or determines the desired gasdischarge rate through input from a detection unit 881 which detects,measures or determines the morphology of the occupant to be protected bythe airbag, the type of occupant, the identification of the occupant,the position of the occupant and/or the severity of the crash. Any ofthese factors, or combinations of these factors, may be used in thedetermination of the discharge rate to optimally protect the occupant ina crash. The discharge rate determination unit 880 and detection unit881 may be used in any of the embodiments described herein.

As shown in FIG. 40B, a motor or other actuating device 876 may rotatethe outer cylinder 875 in the direction of arrow B relative to the innercylinder 874, in which case, the inner cylinder 875 is situated withinthe outer cylinder 875. The openings in the outer cylinder 875 may alignfully with the openings in the inner cylinder 874 (in which case thevalve is in the full discharge position) or align with material betweenthe openings in the inner cylinder 874 (in which case the valve is inthe full blocked-discharge position). Between these extreme positions isa wide range of variations in the discharge of the gas in the airbag.

Instead of having the outer cylinder 875 move relative to the innercylinder 874, the reverse situation could also be used, i.e., move theinner cylinder relative to the stationary outer cylinder, in which case,the outer cylinder would be fixed to the airbag since the stationarycylinder is preferably fixed to the airbag. Also, as shown, the airbaginterior is on the side of the outer cylinder 875 and the airbagexterior is on the side of the inner cylinder 874 so that gas isdischarged from the airbag first through the openings in the outercylinder 875 and then through the openings in the inner cylinder 874.The reverse situation could also be used. Thus, in general, the set ofopenings of one cylinder is in flow communication with the interior ofthe airbag and the set of openings in the other cylinder is in flowcommunication with the exterior of the airbag so that the degree ofregistration or alignment between the openings determines the dischargerate of gas from the airbag.

Referring now to FIGS. 41A and 41B, instead of plates or cylindershaving a pattern of openings interposed between the airbag interior andairbag exterior, a pair of cones could be used.

As shown in FIGS. 41A and 41B, an inner cone 878 has a pattern ofopenings and is positionable inside an outer cone 877. Inner cone 878 iscoupled to a motor 879 or other actuating device for moving the innercone 878 in a stroked manner in the direction of arrow A, in which case,the inner cone 878 is moved up and down relative to the outer cone 877(FIG. 41A). The pattern of openings in the inner cone 878 may completelyalign with the pattern of openings in the outer cone 96 when the innercone 878 is fully in the up position.

In the alternative, as shown in FIG. 41B, the motor or other actuatingdevice 876 may rotate the inner cone 878 in the direction of arrow Brelative to the outer cone 877, in which case, the inner cone 878 issituated almost entirely within the outer cone 877. The openings in theinner cone 878 may align fully with the openings in the outer cone 877(in which case the valve is in the full discharge position) or alignwith material between the openings in the outer cone 877 (in which casethe valve is in the full blocked-discharge position). Between theseextreme positions is a wide range of variations in the discharge.

Instead of having the inner cone 878 move relative to the outer cone877, the reverse situation could also be used, i.e., have the outer conemove relative to the inner cone, in which case, the inner cone would befixed to the airbag since the stationary cone is preferably fixed to theairbag. Also, as shown, the airbag interior is on the side of the outercone 878 and the airbag exterior is on the side of the inner cone 878 sothat gas is discharged from the airbag first through the openings in theouter cone and then through the openings in the inner cone. The reversesituation could also be used. Thus, in general, the set of openings ofone cone is in flow communication with the interior of the airbag andthe set of openings in the other cone is in flow communication with theexterior of the airbag so that the degree of registration or alignmentbetween the openings determines the discharge rate of gas from theairbag.

FIG. 42 is an illustration of a discharge valve including stacked driveelements. A spring 883 biases the cone 884 to the open dischargingposition. A stack of bimorph piezoelectric washers 882 when activatedclose the valve shutting off the flow out of the airbag.

The discharge valves described above can be used individually or incombination in a single airbag. To the extent possible, the dischargevalves can also be connected and controlled by a control system whichtailors the outflow rate through the discharge valve to the propertiesof the occupant. That is, an occupant sensor is provided in the vehicleto measure or determine one or more properties of an occupant and thenthe control system considers the measured or determined properties whendetermining the desired, optimum gas outflow rate and controls thedischarge valve accordingly. The control system may also consider theproperties of the crash as determined by one or more crash sensors andassociated circuitry. Such properties include the velocity change of thecrash, the acceleration of the crash and the direction of impact.

The examples shown generally illustrate the placement of the valve inassociation with the fabric of the airbag, i.e., at a location on oragainst the fabric of the airbag over a discharge opening different fromthe inlet opening of the airbag which is coupled to the inflatorstructure or inflation mechanism of the airbag. Alternately, the valvecan be placed on other structure that is in fluid communication with theinterior of the airbag. Such structure can be part of, for example, theinflator structure or inflator of the airbag.

With respect to the drive elements which move one member having openingsrelative to another, e.g., a plate, cylinder and cone, stacked driveelements could be used. That is, a stack of piezoelectric, ferroelectricor phase change alloy elements may be used to provide a short strokewith a high modulation force and millisecond response time. Also, toincrease response time into the millisecond range, a high force pre-loadwith a mechanical spring and an escarpment mechanism for triggering thedischarge valve could be used. A popit-type valve that uses theavailable air pressure to obtain gain over a single stage valve may bealso be used in accordance with the invention

Any of the valves described in International Patent Publication No.PCT/RU02/00225 could also be used in accordance with the invention inits various forms. This publication describes a safety device installedinside a vehicle having an inflatable airbag having an inlet forreceiving gas filling the airbag to its ready state, and a system forsupplying gas to the airbag, including a gas source, a valve device, anda triggering unit. The valve device is formed by a pneumatic distributorhaving two stable positions: an open position wherein gas from the gassource is fed to the airbag through its inlet, and a closed positionwherein the gas flow through the airbag inlet is interrupted.

Although multiple embodiments of discharge valves are described above,features of each can be used in the other embodiments. Also, a vehiclecan be manufactured with different discharge valves for differentairbags. Airbags including any of the discharge valves described above,or any combinations of the discharge valves described above, are alsowithin the purview of the invention.

The discharge valve of an airbag in accordance with the invention can becontrolled based on any number of criteria, including but not limited tothe morphology of the occupant to be protected by the airbag (e.g.,weight, height, etc.), the position of the occupant (either the currentposition or an extrapolated future position at which the occupant willbe at the time of airbag deployment), the severity of the crashrequiring airbag deployment, the type of occupant (i.e., adult, occupiedor unoccupied child seat, rear-facing child seat, front-facing childseat, child, pet, etc.), the direction of the crash, the position of theseat or any part thereof, and the identification of the occupying itemsin the vehicle. These criteria may be used individually or incombination to determine the appropriate control of the gas dischargerate of the airbag.

The gas discharge rate of the airbag is controlled by controlling themotor or other actuating device. To this end, the operation of the motoris studied to determine the degree of alignment of the openings in themovable member and the fixed member and thus the gas flow through theopenings, if any, for different positions of the movable plate. Then, inoperation, the motor is controlled to move the plate in the requiredmanner to provide for the desired gas discharge rate.

1.9 Airbags with a Barrier Coating

Note most of the following section was taken from U.S. Pat. No.6,087,016 and U.S. Pat. No. 6,232,389 which describe barrier coatings ingeneral but not for application to airbags. Quotation marks have beenomitted for easier reading.

I. Barrier Coating Mixtures

A barrier coating mixture according to this invention includes thefollowing components in a carrier liquid (i.e., aqueous or solvent):

(a) an elastomeric polymer;

(b) a dispersed, exfoliated layered platelet filler having an aspectratio greater than 25; and

(c) at least one optional surfactant, wherein the solids content isdesirably below 30% solids and the ratio of polymer (a) to filler (b) isbetween about 20:1 and 1:1. These barrier coating mixtures result infilms with reductions in permeability of 5 times to 2300 times relativeto the unfilled polymer. These results are substantially higher than theprior art on other platelet filled barrier coatings.

The barrier coating mixtures used in the invention are selected bybalancing several critical features, i.e., appropriate dispersion of thefiller in the elastomeric polymer, orientation of the filler plateletsin the elastomeric polymer, as well as high aspect ratio of the filler,in order to achieve the desired permeability reductions and flexibilityin the dried barrier coating and in the airbags. These characteristicsare demonstrated by the data shown in FIG. 43. The barrier coatingmixture of this invention desirably contains an unusually low solidscontent, i.e., between about 1% and about 30% solids. A more desirablerange of solids content is between about 5% to about 17% solids.

The solids content is an important consideration in the barrier coatingscompositions and performance of the dried coatings because the solidscontent effects the dispersion of the high aspect ratio filler. If ahigh total solids content is used in the barrier coating composition,one would not achieve well-dispersed filler, e.g., vermiculite, and thepermeability reductions characteristic of the coatings of this inventionare not achieved. The preferred range of solid content (5%-17%) isunexpectedly well below that typically used in the coating industry andtherefore not predicted by the prior art teachings concerning barriercoatings formulations. This is especially true of the airbag industrywhere no such fillers are used prior to the teachings of this invention.

The relationship between the percentage of solids in the coatingcomposition to the weight percent of filler in the resulting driedcoating is an unexpectedly important issue in obtaining desired barriercoatings of this invention. For example, in embodiments in which thebarrier coating composition contains as the elastomeric polymer, butylrubber (Lord Corporation), and as the filler, MICROLITE®963++vermiculite solution (W.R. Grace & Co.), FIG. 44 illustrates arange of maximum total solids that can be used in the coatingsformulation of this invention without resulting in agglomeration andother negative effects on the dried coating (i.e., film) properties as afunction of the fraction of the total solids made up by the filler.

In one embodiment, where the MICROLITE® filler is at 5%, the maximumsolids is about 16%; in another wherein the filler is 25%, the maximumsolids is about 9%. In still another embodiment, where the filler isabout 50%, the maximum solids is about 5%. Other examples fall withinthose ranges, as indicated in FIG. 44. The results shown in FIG. 44 arebased on the formulations used in Examples 9-12 set forth in U.S. patentapplication Ser. No. 10/413,318 incorporated by reference herein.

The unusually low solids contents described in FIG. 44 for abutyl-containing polymer latex are also applicable to other elastomericpolymer latexes, as well as to elastomeric polymers in carrier liquidswhich also contain other solvents or co-solvents. One of skill in theart will understand the need to make some alterations in the maximumsprovided by FIG. 44 for other formulations of barrier coatings of thisinvention taking into account changes in electrolyte concentration,surfactants, grade and composition of vermiculite or other filler, andgrade and composition of polymeric latex or other elastomeric polymer ina carrier as described herein.

If desired, the solids content of the barrier coating mixtures can befurther adjusted to levels below the maximums shown in FIG. 44 usingthickeners, in order to adjust the final film thickness, as well as toadjust the suspension rheology. See, for example, Examples 14-15 of the'318 application which demonstrate the increase in viscosity from 4.5 cPto 370 cP using PVOH terpolymer; and Example 16 of the '318 applicationwhich similarly increases viscosity using lithium chloride as athickener. Other conventionally used thickeners may also be useful.

The solids content of the coating mixtures of this invention ispreferably based upon a preferred polymer to filler ratio of betweenabout 20:1 to about 1:1, more preferably 9:1 to 1:1, particularly whenthe polymer is a butyl-containing polymer such as a butyl latex, and thefiller is a vermiculite solution. Examples 9-12 of the '318 applicationindicate a variety of desirable compositions of this inventioncharacterized by a polymer to filler ratios within the above range, overa range of solids contents, polymer contents by weight and fillercontents by weight.

Preferably, in the dried barrier coating (film), the polymer is presentat between about 45 to about 95 by weight and the dispersed layeredfiller is present at between about 5 to about 55% by weight.

A. The Elastomeric Polymer

Elastomeric polymers useful in forming coating mixtures of thisinvention include polymers selected generally from among many classes.The selected polymers may be curable polymers, partially cured polymers,or uncured polymers, and may be soluble in water or a solvent. Suchpolymers include, without limitation, olefinic thermoplastic elastomer(TPO); polyamide thermoplastic elastomer (Polyamide TPE); polybutadienethermoplastic elastomer, e.g., syndiotactic 1,2-polybutadienethermoplastic elastomer (polybutadiene TPE); polyester thermoplasticelastomer (Polyester TPE); polyurethane thermoplastic elastomer (TUPR),for example, thermoplastic polyester-polyurethane elastomer (TPAU), andthermoplastic polyether-polyurethane elastomer (TPEU); styrenicthermoplastic elastomer (Styrenic TPE); vinyl thermoplastic elastomer,e.g., polyvinyl chloride polyol (pPVC).

A variety of rubbery polymers (curable, partially cured, or uncured) mayalso be employed as the polymer component of the present invention,including acrylic rubber, such as ethylene-acrylate copolymer (EACM);and butadiene rubber, such as polybutadiene. Butyl-containing polymersuseful in forming coating mixtures of this invention include, withoutlimitation, curable, partially cured, or uncured polymers: butyl rubber,such as isobutylene-isoprene copolymer (IIR); bromobutyl rubber, e.g.,bromoisobutylene-isoprene copolymer (BIIR); chlorobutyl rubber, e.g.,chloroisobutylene-isoprene copolymer (CIIR); and isobutylene rubber.Butyl rubber is defined as a poly(isobutylene) homopolymer or acopolymer of poly(isobutylene) with isoprene. Modified butyl rubbersinclude halogenated poly(isobutylene) and its copolymers and isoprene.Additional polymers or copolymers that contain more than 50% isobutyleneare also useful in the practice of this invention, for example,poly(isobutylene-co-acrylonitrile), etc. Other butyl-containing polymerswhich are curable, partially cured or uncured, may be readily selectedby one of skill in the art.

Still other useful elastomeric polymers are chlorosulfonatedpolyethylene rubber, e.g., chlorosulfonated polyethylene (CSM);epichlorohydrin rubber, such as polyepichlorohydrin (CO),polyepichlorohydrin copolymer (CO copolymer); ethylene-propylene rubber(EPR), such as ethylene-propylene copolymer (EPM),ethylene-propylene-diene copolymer (EPDM).

Other polymers for such use include fluoroelastomers, such as vinylidenefluoride-hexafluoropropylene copolymer (FKM); natural rubber (NR);neoprene rubber such as polychloroprene (CR); nitrile rubber, such asacrylonitrile-butadiene copolymer (NBR); polyisoprene rubber (PI);polysulfide rubber; polyurethane, such as polyester urethane (AU), andpolyether urethane (EU); propylene oxide rubber; silicone rubber, suchas silicone (MQ), and methylvinyl-fluorosilicone (FVMQ) andstyrene-butadiene rubber, such as styrene-butadiene copolymer (SBR).

The polymer is preferably capable of forming a solution, dispersion,latex, suspension or emulsion in water or a solvent, or a mixturethereof. Specifically exemplified below is a coating mixture of theinvention employing as the elastomeric polymer, butyl latex. A suitablecommercially available butyl latex for use in the compositions of thisinvention is Lord® BL-100 butyl latex, which is a 62% by weight aqueousbutyl latex solution [Lord Corporation]. Another suitable butyl latex,the use of which is illustrated in Example 10 of the '318 application,is Polymer Latex ELR butyl latex, a 50% butyl latex solution (PolymerLatex). Still another suitable polymer is a 51.7% bromo-butyl latexsolution available from Polymer Latex (see Examples 11-12 of the '318application). These latexes contain an ionic surfactant package whichstabilizes the latex and effects the performance of the barrierformulation. Other butyl latexes are anticipated to be similarly usefulif combined with similar ionic surfactants. Preferably, the selectedpolymer is present in the dried coating mixture at a minimum of about45% by weight of the dried compositions.

B. The Filler

The coating mixtures of this invention as described above also include adispersed layered filler which, upon mixture, has an inherently highaspect ratio, which can range from about 25 to as high as about 30,000.The presently preferred filler is vermiculite. More particularly, adesirable vermiculite is MICROLITE® 963++water-based vermiculitedispersion (W. R. Grace) [see, EP Application No. 601,877, publishedJun. 15, 1994] which is a 7.5% by weight aqueous solution of dispersedmica. One novel aspect of the mixtures of the present invention is theeffective aspect ratio of the selected filler in the dried coating.According to this invention, in the dried coating, the filler remainssubstantially dispersed, thereby having a “high effective aspect ratio”,as shown in FIG. 43. FIG. 43 assumes high levels of orientation.

Preferably, the effective aspect ratio of the filler in the compositionsof this invention is greater than 25 and preferably greater than about100, although higher ratios may also be obtained. In embodiments inwhich orientation is not high, the effective aspect ratio required forlarge reductions in permeability will be higher than 100. In the coatingmixtures (the liquid), the layered filler is present at between about 1to about 10% by weight of the total mixture. In the dried coatings ofthis invention, the layered filler is present at a minimum of about 5%by weight to a maximum of about 55% of the dried coating. Thecompositions of the present invention, when dried, retain the filler inwell-dispersed form, resulting in a high effective aspect ratio of thedried coating, and greatly increased reduction in permeability, asillustrated in FIG. 43.

MICROLITE® vermiculite is the preferred filler because of its very highaspect ratio. The vermiculite plates have an average lateral size ofbetween 10 and 30 microns. The plates are largely exfoliated in water,and thus their thickness is 1-2 nm. The aspect ratio of the filler inwater dispersion is an average of 10,000-30,000. It is clear that manyplates reassemble during the coating and drying process of the presentinvention, thus reducing the effective aspect ratio achieved in thefinal coating. However, it is a great advantage to start with as largean aspect ratio as possible.

Although MICROLITE® 963++vermiculite (W. R. Grace) is preferred, goodresults may also be achieved with less exfoliated grades of MICROLITE®vermiculite (i.e., grades 963, 923, and 903). Other layered silicatesare also useful in the barrier coatings and films of this invention. Theeffectiveness of other silicates in the barrier coating of thisinvention depends upon the lateral size of the platelets, the degree ofexfoliation in water, and the degree to which they reassemble to formlarger particles during the coating and drying process. Examples ofother layered silicates include bentonite, vermiculite, montmorillonite,nontronite, beidellite, volkonskoite, hectorite, saponite, laponite,sauconite, magadite, kenyaite, ledikite and mixtures of the abovesilicates. The selection and use of other known silicates which haveproperties similar to those of MICROLITE® vermiculite, as well assufficiently high aspect ratios, are expected to be obvious to one ofskill in the art following the teachings of this invention.

C. Surfactants and Other Additives

Coating mixtures used in the invention, particularly those useful onsurfaces and interfaces according to this invention, also preferablycontain at least one or more suitable surfactant to reduce surfacetension. Surfactants include materials otherwise known as wettingagents, anti-foaming agents, emulsifiers, dispersing agents, levelingagents etc. Surfactants can be anionic, cationic and nonionic, and manysurfactants of each type are available commercially. A suitablesurfactant for inclusion in these compositions possesses a criticalmicelle concentration sufficiently low to ensure a dried coatinguncompromised by residual surfactant.

Preferably, the surfactant(s) useful in the methods and solutions ofthis invention are nonionic, particularly useful with a highly chargedfiller, such as vermiculite. In the event of an unfavorable interactionof the anionic emulsifier present in the butyl latex dispersion [Lord],which is a presently preferred source of the butyl-containing polymer,any additional ionic additives must be kept to a minimum. This variableis eliminated where the surfactant or emulsifier is non-ionic. Increasein ionic concentration of the compositions containing vermiculite, suchas by the addition of a base to adjust pH, e.g., LiOH, NH₄OH, and NaOHcan cause agglomeration of the filler, which adversely affectspermeability reduction.

Some embodiments of this invention include at least two surfactants,which include preferably both a wetting agent and an anti-foaming agent.Still other compositions may have additional surfactants to performadditional effects. Desirable surfactants employed in the examples ofthe '318 application are the non-ionic siloxane-based, Silwet® L-77wetting agent [OSI Specialties, Inc.], the BYK®-306 wetting/levelingagent [BYK Chemie], FOAMASTER® VL defoamer (Henkel), and the DC200®anti-foaming agent [Dow Corning], among others. As exemplified below, anantifoaming agent may be predispersed in solution with, e.g.,1-methyl-2-pyrrolidinone (NMP) because some antifoaming agents are notsoluble in the barrier coating.

Other suitable surfactants may also be selected. The amount and numberof surfactants added to the coating solution or composition will dependon the particular surfactant(s) selected, but should be limited to theminimum amount of surfactant that is necessary to achieve wetting of thesubstrate while not compromising the performance of the dried coating.For example, typical surfactant amounts can be less than or equal toabout 10% by weight of the dried coating.

In another embodiment, thickeners may be used in the coatingformulations to adjust viscosity. Such thickeners may include, withoutlimitation, a polyvinyl alcohol (PVOH) terpolymer, e.g.,polyvinylbutyral/polyvinylacetate/polyvinylalcohol or a lithium chloridethickener. In one embodiment, the viscosity of the coating mixture canbe increased from 4.5 cP to 370 cP with the addition of the PVOHterpolymer to the formulation as illustrated in Examples 14-15 of the'318 application. For example, for a coating mixture containing 10%total solids with 2% MICROLITE® vermiculite formulation, a thickenersuch as PVOH terpolymer can be added in an amount of between about 3% toabout 5.5% by weight. Desirably the thickener is added in an amount ofgreater than 3.5% by weight. A preferred range of thickener is betweenabout 5 and 5.5% by weight.

It has been noted that greater than 5.5% by weight of PVOH terpolymerthickener can cause agglomeration of the filler platelets. As anotherexample, the viscosity of the coating mixture can also be increased withthe addition of lithium chloride as a thickener to the coating mixture,(See e.g., Example 16 of the '318 application). For example, for acoating mixture containing 10% total solids with 2% MICROLITE®, thethickener is employed in an amount between about 3% to about 5% byweight. Desirably greater than 4% thickener is employed, and moredesirably 5% thickener is employed. Greater than 5% by weight of thelithium chloride thickener produces poor barrier properties. One ofskill in the art would readily determine and adjust the type and amountsof thickener depending on the type and amount of filler employed in thecoating mixture based on the teachings contained herein.

Still other optional components of the barrier coating are componentswhich effect curing of the coating. For example, one type of cure“package” contains about 10 to about 30% by weight zinc oxide, about 5to about 20% by weight sulfur, about 30 to about 60% by weight water,about 0.1 to about 10% of a dispersing agent, about 5 to about 20% ofzinc dibutyldithio-carbamate and about 1 to about 10% zinc2-mercaptobenzothiazole. The amount of cure package added to the coatingmixture is based on the amount of butyl rubber in the coating mixture.

In one embodiment, greater than 10 parts dried cure package is added per100 parts butyl rubber in the coating mixture. A desirable amount ofdried cure package is about 15 parts cure package per 100 parts butylrubber in the mixture. One of skill in the art can readily design a cure“package” to enhance the curing of a butyl latex barrier coating mixtureof this invention, and select a desirable amount to be added to thecoating mixture, based on the teachings of this specification combinedwith the knowledge of the art. See, e.g., U.S. Pat. No. 4,344,859.

D. The Carrier Liquid

The coating mixtures of this invention are present in a suitable carrierliquid. Carriers which are suitable for use in the composition of thisinvention include, without limitation, water and solvents such ashexane, heptane, toluene, 1 methyl-2-pyrrolidinone, cyclohexanone,ethanol, methanol, and other hydrocarbons. Combinations of water with anorganic carrier may also be used as the carrier liquid. Selection of asuitable organic solvent carrier is within the skill of the art.

E. Specific Embodiments of Barrier Mixtures

One example of a barrier coating mixture useful for application tosubstrates such as a fabric portion of an airbag and in particular aside curtain airbag according to this invention comprises coating formedby a barrier coating mixture comprising in a carrier liquid: (a) anelastomeric polymer; (b) a dispersed exfoliated layered platelet fillerpreferably having an aspect ratio greater than 25; and optionally (c) atleast one surfactant. The elements are selected so that the solidscontent of the mixture is less than about 30% and the ratio of thepolymer to the filler is preferably between about 20:1 and about 1:1.These barrier coating mixtures result in films with reductions inpermeability of 5 times to 2300 times relative to the unfilled polymer.These results are substantially higher than the prior art on otherplatelet filled barrier coatings or any airbag coatings.

Another barrier coating mixture which is desirable for application to afabric portion of an airbag according to this invention includes thefollowing components in a carrier liquid, (a) a butyl-containing polymerlatex; (b) a dispersed exfoliated layered vermiculite filler preferablyhaving an aspect ratio about 1000 or greater; and optionally (c) atleast one surfactant. The components are selected such that the solidscontent of the mixture is less than abut 17% and the ratio of thepolymer to the filler is between about 20:1 and about 1:1.

In a preferred embodiment, the coating mixtures described above havesolids contents of between about 5% to about 15% by weight, and formdried coatings on the airbag surface that comprise between about 45% toabout 95% by weight of the polymer, between about 5% to about 55% byweight of the filler, and between about 1.0% to about 10% by weight ofthe surfactant(s). The dried coatings of the mixtures described above,contain fillers which preferably exhibit an effective aspect ratio ofgreater than about 25, reduces the gas, vapor or chemical permeabilitygreater than 5-fold that of the dried, unfilled polymer alone.Preferably, the effective aspect ratio of the dried coatings is greaterthan about 50, and even greater than about 100.

One preferred coating mixture useful in this invention has a solidscontents of between about 5% to about 15% by weight and the driedcoating comprises between about 65% to about 90% by weight of abutyl-containing polymer latex, between about 10% to about 35% by weightof a vermiculite filler, between about 0.1% to about 0.10% by weight ananti-foaming agent as surfactant, with the total surfactant weightpercent up to about 15%. As described in examples in the '318application, the selected polymer is the elastomer butyl rubber or butyllatex, e.g., Lords BL-100 butyl latex in a 62% by weight aqueous butyllatex solution [Lord Corporation]. Additional preferred barrier coatingmixtures useful in this invention may be prepared by methods describedin detail in Examples 1-12 and 14-16 of the '318 application.

2. The Coated Article

Once prepared as described in detail in the Examples in the '318application, the coating mixtures may be applied to a portion of fabricwhich will be incorporated into or sewn to form an airbag of a vehicle,to reduce the permeability of the fabric to gas, vapor (moisture) orchemicals. The dried coating, in which the filler exhibits an effectiveaspect ratio of greater than about 25, reduces the gas, vapor orchemical permeability greater than 5-fold that of the dried, unfilledpolymer alone. In the dried coating, more preferably, the polymer ispresent in the mixture when dried at a weight percent of at least about45%. The filler is preferably present in the mixture when dried atgreater than about 5% by weight. These barrier films achieve reductionsin permeability of 5 times to 2300 times relative to the unfilledpolymer. These results are substantially higher than the prior art onother platelet filled elastomers.

Preferably, the effective aspect ratio of the dried coating is greaterthan about 50, and even greater than about 100. As indicated in Examples1-12 of the '318 application, reductions in permeability attributed tocompositions of this invention can range from approximately 5 times to2300 times that of unfilled polymer alone.

The coating compositions used in the invention may be applied on theinside of the fabric, i.e., on a portion of the fabric which, once theairbag is formed, will face the interior gas-receiving compartment ofthe airbag. The coating is applied by standard techniques, with spraycoating and dip coating likely to be the most effective.

The present invention substantially reduces the weight of a side curtainairbag, for example, by providing equivalent sealing of the fabricthereby reducing the flow of the inflation gas through the materialusing substantially less sealing material. Typically, the weight of thesealant is reduced by a factor of five or more. However, much of theleakage occurs through the seams and sealing the fabric will not reducethis leakage. Most side curtain airbags are currently sealed at theedges by sewing or interweaving where the entire airbag is woven atonce. In the first case, the sewing threads make holes in the fabric andserve as a path for gas leakage. In the second case, interweavingresults in a leakage path since when the airbag is pressurized thestresses in the seams separate the threads at the joints again creatingleakage paths. A preferred method is to heat or adhesive seal the piecesof fabric together and to do so over an extended seam width therebyeliminating the leakage paths. Since such seals are often weaker than asewn or woven seam, careful attention must be given to the design of theairbag chambers to prevent stress concentrations in the seams. Thisfrequently requires a finite analysis and redesign of the individualchambers in order to eliminate such stress concentrations.

The airbag may be formed completely by interweaving, heat sealing orsewing of the layers before the barrier coating is applied. Currently,airbags are often formed this way but without a barrier coating. Ingeneral, any known technique for manufacturing an airbag can be appliedto make an airbag in accordance with the invention, i.e., an airbag madeof one or more substrates and a barrier coating.

A selected barrier coating mixture, such as those described above may beapplied to a surface or interface of a fabric section to be incorporatedinto an airbag to accomplish a variety of purposes in the airbagmanufacturing industries to reduce the permeability of the airbag togas, vapor or chemicals.

3. Methods of Coating a Substrate or Forming a Film

The fabric sections to be coated by the compositions of the inventionmay be previously untreated or may have a variety of pre-treatments totheir surfaces. For example, the fabric sections may have on at leastone side a heat seal layer. Such heat seal layers may be made of anethylene-propylene copolymer or ethylene-propylene-butylene terpolymer.Thus, the coating solution is applied on the surface of the heat seallayer. Alternatively, the fabric sections may comprise a protectivetopcoat layer, such as polyurethane or Teflon®-type materials [DuPont]for abrasion resistance, etc. Such topcoats may be selected by one ofskill in the art. The coatings of this invention may be applied over orunder the topcoat layer.

Alternatively, the article may be cured prior to application of thecoating, or it may be cured following application of the coating on theappropriate surface.

To form the coated article of this invention, the application of theselected barrier coating mixture may be accomplished by techniquesincluding, without limitation, roller transfer or paint coating, spraycoating, brush coating and dip coating. Roll coating techniques include,but are not limited to, rod, reverse roll, forward roll, air knife,knife over roll, blade, gravure and slot die coating methods. Generaldescriptions of these types of coating methods may be found in texts,such as Modern Coating and Drying Techniques, (E. Cohen and E. Gutoff,eds; VCH Publishers) New York (1992) and Web Processing and ConvertingTechnology and Equipment, (D. Satas, ed; Van Nostrand Reinhold) New York(1984). Three dimensional articles may preferably be coated by thetechniques which include, but are not limited to, spray coating or dipcoating. The method of application is not a limitation on the presentinvention, but may be selected from among these and other well-knownmethods by the person of skill in the art. However, the coating must beapplied so that drying takes place on the substrate and not in the air(i.e. powder coating). If drying takes place during spraying or othermeans of application, agglomeration may occur.

The coating mixtures may be applied to a fabric substrate, such as anexterior or interior surface, an interface, or component of the airbag,at any desired thickness. Thus, for example, the coating mixtures of thepresent invention may be applied to the surface of fabric sections bythe methods described above to form a dried coating of a thicknessbetween about 0.1 (m to about 100 (m of dry coating. Such adjustments tothickness are well within the skill of the art [see, e.g., CanadianPatent No. 993,738].

After coating, the coated airbag, may be dried at a selectedtemperature, e.g., room temperature or greater than room temperature.The selection of the drying temperature, relative humidity, andconvective air flow rates depends on the desired time for drying; thatis, reduced drying times may be achieved at elevated air temperatures,lower relative humidity and higher rates of air circulation over thedrying coating surface. After drying, the exfoliated silicate fillerparticles are oriented within the elastomeric latex (solution, emulsion,etc.) to a high degree parallel to each other and to the airbagsubstrate surface. One of skill in the art can readily adjust the dryingconditions as desired. The performance of the dried barrier coating isinsensitive to drying temperatures over the range 25-160° C.

The dried coatings exhibit a surprising reduction in permeabilitycompared to the prior art and particularly compared to unfilledpolymers.

The dried coating preferably maintains its low permeability afterrepeated mechanical loading and elongation up to about 10% of theairbag. The evaluation of the coating integrity after exposure torepeated loading and elongation was examined as described in Example 17of the '318 application.

The coatings and methods of the present invention described above may beapplied to the manufacture or repair of airbags to improve air or gasretention. The barrier coatings may allow reduced mass, reduced gaspermeability resulting in better air retention, reduced thermo-oxidativedegradation, and enhanced wear and elongation of the useful life of thearticle.

Referring now to FIGS. 45, 46, 477A and 47B, an airbag module inaccordance with the invention is designated generally as 890 andcomprises a module housing 891 in which an airbag 892 is folded. Thehousing 891 may be arranged in any vehicle structure and includes adeployment door 893 to enable the airbag to deploy to protect theoccupants of the vehicle from injury. Thus, as shown, the housing 891may be mounted in the ceiling 894 of the vehicle passenger compartment895 to deploy downward in the direction of arrow A as a side curtainairbag to protect the occupants during the crash.

As shown in FIG. 47A, one embodiment of the airbag 892 comprises asubstrate 896 and a barrier coating 897 formed on the substrate 896,either on the inner surface which will come into contact with theinflation fluid or on an outer surface so that the barrier coating 897will come into contact only with inflation fluid passing through thesubstrate 895. The airbag 892 may be formed with any of the barriercoatings described herein. In one embodiment, a flat sheet of thesubstrate 896 would be coated with the barrier coating 897 and then cutto form airbags having an edge defining an entry opening for enablingthe inflation of the airbag. The edge 898 of the airbag 892 would thenbe connected, e.g., by sealing, to a part 899 of the housing 891 whichdefines a passage through which the inflation fluid can flow into theinterior of the airbag 892 (see FIG. 46). The inflation fluid may begenerated by an inflator 900 possibly arranged in the module housing891.

In the embodiment shown in FIG. 47B, the barrier coating 897 is placedbetween two substrates 896, 901. Any number of substrates and barriercoatings can be used in the invention. Also, the number of substratesand barrier coatings can be varied within a single airbag to provideadditional substrates and/or barrier coatings for high stresses areas.

Referring now to FIG. 48, a method for designing a side curtain airbagin accordance with the invention will now be described. It is a problemwith side curtain airbags that since they are usually formed of twopieces of material, the manner of connecting the pieces of materialresults in leakage at the seams.

To avoid this problem, in the invention, two pieces of material, forexample, a piece of fabric with a barrier coating as described herein,are cut (step 902) and edges of the two pieces are sealed together toform an airbag while leaving open an entry opening for inflation fluid(step 903). The location of partition lines for partitioning the airbaginto a plurality of compartments, e.g., a plurality of parallelcompartment each of which is receivable of inflation fluid and adaptedto extend when inflated vertically along the side of the vehicle, isdetermined (step 904) and it is determined whether the stresses are atthe seams (step 905). If not, the design is acceptable (step 906).Otherwise, the airbag is re-designed until stresses are not created atthe seams during inflation or a minimum of stress is created at theseams during inflation. The determination of the location of thepartition lines may involve analysis of the airbag using finite elementtheory.

This embodiment of the invention is illustrated by non-limiting examples(Examples 1-17) set forth in U.S. patent application Ser. No.10/413,318, which is incorporated by reference herein.

2. Summary

Disclosed is above a method for manufacturing an airbag for a vehicle inwhich a plurality of sections of material are joined together to form aplurality of interconnected compartments, e.g., by applying an adhesivebetween opposed surfaces of the sections of material to be joinedtogether or heating the sections of material to be joined together. Thesections of material may be joined together along parallel or curvedlines to form straight or curved, elongate interconnected compartmentswhich become tubular or cellular when inflated with a gas.

The tear propagation arresting structure for the film sheets may be (i)the incorporation of an elastomeric film material, a laminated fabric,or net, which are connected to each of the pieces of plastic film (e.g.,the inelastic film which provides the desired shape upon deployment ofthe airbag), or (ii) structure incorporated into the formulation of theplastic film material itself. Also, the two pieces of film may be formedas one integral piece by a blow molding or similar thermal forming orlaminating process.

In accordance with another embodiment of the invention, an airbag has acoating composition which contains substantially dispersed exfoliatedlayered silicates in an elastomeric polymer. This coating, when dry,results in an elastomeric barrier with a high effective aspect ratio andimproved permeability characteristics, i.e., a greater increase in thereduction of permeability of the coating. Drying may occur naturallyover time and exposure to air or through the application of heat. Thisis a further use of a plastic film where although the mechanicalproperties of the base material are not altered the flow propertiesthrough the material are.

The airbag is optionally made of fabric and can take any form includingthose in the prior art. For example, if a side curtain airbag, then theairbag can define a series of tubular gas-receiving compartments, oranother series of compartments. The side curtain airbag can be arrangedin a housing mounted along the side of the vehicle, possibly entirelyabove the window of the vehicle or partially along the A-pillar of thevehicle.

The side curtain airbag includes opposed sections or layers of material,either several pieces of material joined together at opposed locationsor a single piece of material folded over onto itself and then joined atopposed locations. Gas is directed into the compartments from a gasgenerator or a source of pressurized gas. Possible side curtain airbagsinclude those disclosed in the current assignee's U.S. Pat. No.5,863,068, U.S. Pat. No. 6,149,194 and U.S. Pat. No. 6,250,668.

The invention is not limited to side curtain fabric airbags and otherfabric airbags are also envisioned as being encompassed by theinvention. Also, it is conceivable that airbags may be made of materialsother than fabric and used with a barrier coating such as any of thosedisclosed herein and other barrier coatings which may be manufacturedusing the teachings of this invention or other inventions relates tobarrier coatings for objects other than airbags. Thus, the invention canencompass the use of a barrier coating for an airbag, regardless of thematerial of the airbag and its placement on the vehicle.

In one aspect, the present invention provides a side curtain airbagincluding one or more sheets of fabric that contains air or a gas underpressure, and having on an interior or exterior surface of the fabricsheet(s) a barrier coating formed by applying to the surface a mixturecomprising in a carrier liquid an elastomeric polymer, a dispersedexfoliated layered platelet filler preferably having an aspect ratiogreater than about 25 and optionally at least one surfactant. The solidscontent of the mixture is optionally less than about 30% and the ratioof polymer to the filler is optionally between about 20:1 and about 1:1.The coating may be dried on the coated surface, wherein the driedbarrier coating has the same polymer to filler ratio as in the mixtureand provides an at least 5-fold greater reduction in gas, vapor,moisture or chemical permeability than a coating formed of the unfilledpolymer alone.

In a preferred embodiment, the fabric is coated with a barrier coatingmixture, which contains the polymer at between about 1% to about 30% inliquid form and between about 45% to about 95% by weight in the driedcoating. The dispersed layered filler is present in the liquid coatingmixture at between about 1% to about 10% by weight, and in the driedcoating formed thereby, at between about 5% to about 55% by weight. Thedried coating, in which the filler exhibits an effective aspect ratio ofgreater than about 25, and preferably greater than about 100, reducesthe gas, vapor or chemical permeability greater than 5-fold that of thedried, unfilled polymer alone.

In another preferred embodiment, the invention provides a fabric sidecurtain airbag coated with a preferred barrier coating mixture which hasa solids contents of between about 5% to about 15% by weight, andcomprises in its dried state between about 65% to about 90% by weight ofa butyl rubber latex, between about 10% to about 35% by weight of alayered filler, desirably vermiculite, and between about 0.1% to about15% by weight of a surfactant.

In another embodiment, the invention provides a fabric side curtainairbag on a surface or at the interface of two surfaces therein a driedbarrier coating formed by a barrier coating mixture comprising in acarrier liquid, an elastomeric polymer, a dispersed exfoliated layeredplatelet filler preferably having an aspect ratio greater than about 25and optionally at least one surfactant, wherein the solids content ofthe mixture may be less than about 30% and the ratio of polymer to thefiller is optionally between about 20:1 and about 1:1. When dried, thecoating optionally comprises about 45% to about 95% by weight of thepolymer, between about 5% to about 55% by weight the dispersed layeredfiller; and between about 1.0% to about 15% by weight the surfactant.The coating on the article, in which the filler exhibits an effectiveaspect ratio of greater than about 25, preferably greater than about100, reduces the gas, vapor or chemical permeability of the airbaggreater than 5-fold the permeability of the airbag coated with thepolymer alone.

In still another embodiment, the invention provides a fabric sidecurtain airbag having on a surface or at the interface of two surfacestherein a dried barrier coating formed by a barrier coating mixturecomprising in a carrier liquid, a butyl-containing polymer latex, adispersed exfoliated layered vermiculite filler preferably having anaspect ratio about 1000 or greater; and optionally at least onesurfactant. The solids content of the mixture may be less than about 17%and the ratio of the polymer to the filler may be between about 20:1 andabout 1:1.

In a preferred embodiment, the coating mixture has a solids content ofbetween about 5% to about 15% by weight, and forms a dried coating onthe surface that comprises between about 65% to about 90% by weight thebutyl-containing polymer, between about 10% to about 35% by weight thevermiculite filler, and between about 1.0% to about 15% by weight thesurfactant. The coating on the inflated product in which the fillerexhibits an effective aspect ratio of greater than about 25, preferablygreater than about 100, reduces the gas, vapor or chemical permeabilityof the airbag greater than 5-fold the permeability of the article coatedwith the polymer alone.

In still a further embodiment, the invention provides a method formaking a fabric side curtain airbag, the method involving coating asurface of the fabric airbag with, or introducing into the interfacebetween two surfaces of the fabric airbag, an above-described barriercoating mixture.

One method for manufacturing an airbag module including an airbag inaccordance with the invention entails applying to a surface of asubstrate a solution comprising an elastomeric polymer and a dispersedexfoliated layered filler and causing the solution to dry to therebyform a barrier coating on the substrate, forming an airbag having anedge defining an entry opening for enabling the inflation of the airbagfrom the substrate having the barrier coating thereon, arranging theairbag in a housing, sealing the edge of the airbag to the housing andproviding a flow communication in the housing to allow inflation fluidto pass through the entry opening into the airbag. The airbag ispreferably folded in the housing. The airbag may be formed by cuttingthe substrate to the desired shape and size.

Another method for manufacturing an airbag module entails applying to asurface of a first substrate a solution comprising an elastomericpolymer and a dispersed exfoliated layered filler, covering the solutionwith a second substrate, causing the solution to dry to thereby form abarrier coating between the first and second substrates, forming anairbag having an edge defining an entry opening for enabling theinflation of the airbag from the first and second substrates having thebarrier coating therebetween, arranging the airbag in a housing andsealing the edge of the airbag to the housing. Further, a flowcommunication is provided in the housing to allow inflation fluid topass through the entry opening into the airbag. The airbag may be foldedin the housing. The formation of the airbag may involve cutting thefirst and second substrates having the barrier coating therebetween.

Another method for forming an airbag, in particular a side curtainairbag or another type of airbag made of a first piece for fabricconstituting a front panel of the airbag and a second piece of fabricconstituting a rear panel of the airbag, entails heat or adhesivesealing the first and second pieces of fabric together over an extendedseam width to form an airbag while maintaining an entry opening forpassage of inflation fluid into an interior of the airbag andpartitioning the airbag along partition lines into a plurality ofchambers each receivable of the inflation fluid. The location of thepartition lines is determined to prevent concentration of stress in theseams, e.g., by analyzing the airbag using finite element analysis asdescribed in Appendix 1 of the '919 application and Appendices 1-6 ofthe '379 application. The first and second pieces of fabric may becoated with a barrier coating.

Still another method for forming an airbag in accordance with theinvention comprises the steps of providing a plurality of layers ofmaterial, interweaving, heat sealing or sewing the layers together toform the airbag while maintaining an entry opening for passage ofinflation fluid into an interior of the airbag and coating the airbagwith a barrier coating. The airbag may be a side airbag with front andrear panel joined together over an extended seam width. As such, it ispossible to partition the airbag along partition lines into a pluralityof chambers each receivable of the inflation fluid and determine thelocation of the partition lines to prevent concentration of stress inthe seams.

There has thus been shown and described an airbag system with aself-limiting and self-shaping airbag which fulfills all the objects andadvantages sought after. Further, there has been shown and described anairbag system with a film airbag utilizing a film material whichcomprises at least one layer of a thermoplastic elastomer film materialwhich fulfills all the objects and advantages sought after. Manychanges, modifications, variations and other uses and applications ofthe subject invention will, however, become apparent to those skilled inthe art after considering this specification and the accompanyingdrawings which disclose the preferred embodiments thereof. All suchchanges, modifications, variations and other uses and applications whichdo not depart from the spirit and scope of the invention are deemed tobe covered by the invention which is limited only by the followingclaims. For example, the present invention describes numerous differentairbag constructions as well as different methods for fabricatingairbags. It is within the scope of the invention that all of thedisclosed airbags can, for the most part, be made by any of the methodsdisclosed herein. Thus, in one typical process for constructing a filmairbag having at least two compartments, either isolated from oneanother, within one another or in flow communication with each other, atleast one flat panel of film airbag material is provided and thenmanipulated, processed or worked to form the different compartments.More particularly, the flat panel is joined at appropriate locations toform the different compartments, e.g., by heat sealing or an adhesive.The compartments may be any shape disclosed herein, e.g.,tubular-shaped.

With respect to the construction of the airbag as shown in FIGS. 4C and4D, another method of obtaining the airbag with a variable thickness isto provide an initial, substantially uniformly thick film substrate(inelastic film) and thereafter applying a coating (a thermoplasticelastomer) thereon in predetermined locations on the substrate,preferably in an organized predetermined pattern, such that it ispossible to obtain thicker portions in comparison to other uncoatedportions. In this manner, the film airbag can be provided with distinctthicknesses at different locations, e.g., thicker portions whichconstitute rings and ribs (i.e., the polar symmetric pattern of FIG.4C), or only at specific locations where it is determined that higherstresses arise during deployment for which reinforcements by means ofthe thicker film is desired. An alternative fabrication method would beto produce the airbag from thermoplastic elastomeric material with aninitial varying thickness as well as a layer of inelastic film toprovide the airbag with the desired shape. In this regard,plastic-manufacturing equipment currently exists to generate a plasticsheet with a variable thickness. Such equipment could be operated toprovide an airbag having thicker portions arranged in rings and ribs asshown in FIG. 4C.

The limiting net described above may be used to limit the deployment ofany and all of the airbags described herein, including embodimentswherein there is only a single airbag.

This application is one in a series of applications covering safety andother systems for vehicles and other uses. The disclosure herein goesbeyond that needed to support the claims of the particular inventionthat is claimed herein. This is not to be construed that the inventorsare thereby releasing the unclaimed disclosure and subject matter intothe public domain. Rather, it is intended that patent applications havebeen or will be filed to cover all of the subject matter disclosedabove.

The inventions described above are, of course, susceptible to manyvariations, modifications and changes, all of which are within the skillof the art. It should be understood that all such variations,modifications and changes are within the spirit and scope of theinventions and of the appended claims. Similarly, it will be understoodthat applicant intends to cover and claim all changes, modifications andvariations of the examples of the preferred embodiments of the inventionherein disclosed for the purpose of illustration which do not constitutedepartures from the spirit and scope of the present invention asclaimed.

Although several preferred embodiments are illustrated and describedabove, there are possible combinations using other geometries, materialsand different dimensions for the components and different forms of theneural network implementation that perform the same functions. Also, theneural network has been described as an example of one patternrecognition system. Other pattern recognition systems exist and stillothers are under development and will be available in the future. Such asystem can be used to identify crashes requiring the deployment of anoccupant restraint system and then, optionally coupled with additionalinformation related to the occupant, for example, create a system thatsatisfies the requirements of one of the Smart Airbag Phases. Also, withthe neural network system described above, the input data to the networkmay be data which has been pre-processed rather than the rawacceleration data either through a process called “feature extraction”,as described in Green (U.S. Pat. No. 4,906,940) for example, or byintegrating the data and inputting the velocity data to the system, forexample. This invention is not limited to the above embodiments andshould be determined by the following claims.

1. An airbag deployment system for a vehicle having a passengercompartment, comprising: a plurality of airbags arranged tosubstantially fill the passenger compartment upon deployment; aninflator system for inflating said airbags; and a crash sensor systemcoupled to said inflator system for directing said inflator system toinflate said airbag.
 2. The system of claim 1, further comprising aplurality of housings arranged around the passenger compartment, each ofsaid housings including at least one airbag.
 3. The system of claim 1,wherein some of said airbags are interconnected to provide a primaryairbag and at least one secondary airbag extending from said primaryairbag.
 4. The system of claim 1, wherein said inflator system is anaspirated inflator system.
 5. The system of claim 1, wherein said crashsensor system is an anticipatory sensor system.
 6. The system of claim1, wherein said airbags are film airbags.
 7. The system of claim 1,further comprising one-way valves arranged between adjacent ones of saidairbags.